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We have purified and isolated a novel, hypotensive peptide from avian ventricular tissue. Ventricular homogenates have been shown to exhibit potent hypotensive activity in the avian and mammalian species, with little natriuresis or diuresis. Using avian mean arterial pressure (MAP) as a bioassay, we were able to purify a peptide which decreased MAP 30% in adult, female chickens. Amino acid analysis indicated that it contained 20 amino acids (including two cysteine residues), and was not similar to the amino acid composition of mammalian atrial natriuretic factors, or other known hypotensive peptides.

1. To investigate the mechanisms leading to enhanced synthesis and release of atrial natriuretic factor during chronic hypoxia, we measured immunoreactive plasma atrial natriuretic factor, blood gases, packed cell volume, pulmonary artery pressure and systemic artery pressure in male Sprague-Dawley rats exposed to 1, 2 or 3 weeks of normobaric hypoxia. Rats were implanted with pulmonary and carotid artery catheters and studied conscious, 23 h after return to hypoxia. 2. The concentration of atrial natriuretic factor messenger RNA was measured in the right and left ventricular free walls of rats exposed to 3 weeks of hypoxia and in normoxic control rats. 3. There was a trend for plasma atrial natriuretic factor to increase with the duration of exposure to hypoxia but only the 3-week hypoxic rats had a significantly higher level (1080 +/- 193 pg/ml) than the normoxic control rats (318 +/- 46 pg/ml, P less than 0.05, mean +/- SEM). When all the data from normoxic and hypoxic rats were considered together, plasma atrial natriuretic factor was positively correlated with packed cell volume (r = 0.66, P less than 0.001), pulmonary artery pressure (r = 0.68, P less than 0.002), and the index of right ventricular hypertrophy (r = 0.54, P less than 0.01), but after analysis of partial correlation, packed cell volume was the only independent contributing factor to the variance in the level of plasma atrial natriuretic factor (r2 = 0.24).(ABSTRACT TRUNCATED AT 250 WORDS)

A two-dimensional map of human heart left ventricular proteins for 213 polypeptide fractions has been constructed. A quantitative analysis of variability of the fraction position at 60 selected spots with the use of a CVIT computer system revealed a high reproducibility of the material distribution on electrophoregrams. Differences were found in the protein composition of eight heart muscle atrial and ventricular polypeptide fractions. Left ventricular proteins were shown to be represented by six electrophoretical variants. The methodological peculiarities of construction at the two-dimensional map of heart muscle proteins are discussed.

Pattern of myosin light chain in human atrium and ventricles was studied using two-dimensional electrophoresis. Minor fraction was found in ventricles and atria of adult man that coincided in molecular weight, isoelectric point and staining specificity with fetal myosin light chain. The 23 kDa and 24 kDa fractions of auricles were not detected in ventricles.

STUDY OBJECTIVE - The aim of the study was to determine the changes in the beta adrenergic system induced by cardiac hypertrophy due to valvular aortic stenosis. DESIGN - Density of beta adrenoceptors, cardiac tissue noradrenalime concentrations, coronary blood flow (using radioactive microspheres), and haemodynamic variables were compared in a model of experimental aortic valve stenosis of 6 month's duration and in sham operated controls. SUBJECTS - 14 mongrel dogs with aortic stenosis and eight sham operated litter mates were used in the studies. MEASUREMENTS and RESULTS - Heart weight to body weight ratio was 33% greater in dogs with aortic valve stenosis than in controls. There were no haemodynamic differences except for a left ventricular to aortic systolic pressure gradient of 38 (SD 22) mm Hg in the aortic stenosis group. Response of left ventricular dP/dtmax to dopamine was similar in the two groups, as was coronary flow. Density of beta adrenoceptors (Bmax) as measured by (125I)-iodopindolol binding was reduced in ventricles from the aortic stenosis group compared to control: 41.2(13.3) v 59.1(8.1) fmol.mg-1 protein, p less than 0.005. Affinity of receptor for ligand (Kd) was not affected by cardiac hypertrophy. Tissue noradrenaline concentration was reduced in the hypertrophy group: 1108(402) (control) v 438(13) ng.g-1 initial wet weight (aortic stenosis), p less than 0.05. There were no significant subepicardial v subendocardial differences in any variable. CONCLUSIONS - Cardiac hypertrophy induced by aortic valve stenosis over a 6 month period is accompanied by a decrease in the density of ventricular beta adrenoceptors per gram and a decrease in ventricular noradrenaline concentration, though responsiveness of the whole heart is maintained.

Antigen-induced histamine release from sensitized cardiac tissue has been shown to contribute significantly to the increases in atrial rate, atrioventricular nodal conduction, and ventricular contractile force that occur during cardiac anaphylaxis. These findings suggest that there might be a strong negative correlation between changes in these variables and the residual histamine content in the tissue after the anaphylactic reaction. In the present study using isolated hearts of passively sensitized guinea pigs, antigen challenge evoked transient increases in atrial automaticity, P-R intervals, vascular resistance, and left ventricular pressure. The histamine content of atrial and ventricular tissue from antigen-challenge hearts (1,475 +/- 296 and 4,543 +/- 360 ng/g, respectively) was significantly less than that of nonchallenged hearts (2,652 +/- 335 and 6,298 +/- 251 ng/g, respectively). Significant correlations found were between the residual histamine content of the ventricular tissue or the total histamine released and the magnitude of the antigen-induced increase in left ventricular systolic pressure. These findings suggest that antigen-induced increases in left ventricular systolic pressure can be used as an index of the local ventricular histamine release. The lack of significant correlations between local residual histamine levels and changes in atrial rate, P-R intervals, or coronary vascular resistance suggests that complicated interactions between histamine and other mediators or factors may be involved in the antigen-induced chronotropic, dromotropic, and vasoconstrictive alterations in these preparations.

Persistent Mg2+ deficiency may interfere with restoration of normal tissue K+ levels. This study examined: a) the effects of chronic furosemide treatment on K+ of sartorius, aorta and ventricle of rats fed Mg2(+)-deficient (100 ppm) or Mg2(+)-sufficient (400 ppm) diet and deionized water; b) whether normal tissue K+ is restored by oral K+ or K+/Mg2+ supplementation with continued furosemide therapy. Levels of Mg2+ were also measured. Furosemide (20 mg/kg i.p.) decreased K+ in sartorius, aorta and ventricle by 5.5, 4.3 and 19.9 microEq/gm (p less than .05), respectively, in rats fed 100 ppm Mg2+ diet. Furosemide did not alter K+ levels in rats fed 400 ppm Mg2+ diet. K+ supplementation (1 mEq/kg for 7 days) restored K+ to normal in sartorius but the addition of Mg2+ supplementation was necessary to restore K+ levels to normal in ventricle and aorta. These data indicate that furosemide can decrease tissue K+ in rats on a Mg2(+)-deficient diet. This decrease can be reversed during diuretic administration by K+ supplementation in sartorius, or K+ plus Mg2+ supplementation in ventricle and aorta.

We assessed the changes in atrial natriuretic peptide (ANP) and its messenger RNA (mRNA) levels in atria and ventricles in relation to hemodynamic factors during antihypertensive treatments in two-kidney, one-clip renovascular hypertensive rats (RHRs). Hypertension of 10-week duration caused a twofold increase in the left ventricular weight/body weight ratio, a significant increase in left ventricular end-diastolic pressure, and an eightfold increase in left ventricular ANP mRNA levels in RHRs, as compared with the levels in control rats. Uninephrectomy or 4 weeks of treatment with the converting enzyme inhibitor enalapril reduced the blood pressure to the control level, with the complete reversal of left ventricular hypertrophy, left ventricular end-diastolic pressure, and ANP mRNA levels. Four weeks of treatment with the arterial vasodilator hydralazine significantly, but not completely, reduced the high blood pressure, but it did not influence left ventricular hypertrophy, end-diastolic pressure, and ANP mRNA levels. The increased ANP synthesis observed in the right ventricles of RHRs also reverted to the control level by uninephrectomy or enalapril treatment, but not by hydralazine, with a time course similar to that of left ventricular ANP. In addition, uninephrectomy caused the left and right ventricular ANP and ANP mRNA levels of RHRs to fall to the levels of control rats as early as 1 week, despite persistent left ventricular hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)

The development of the ventricular conducting tissue of the embryonic chicken heart has been studied using a previous finding that morphologically recognizable atrial conducting tissue coexpresses the atrial and the ventricular myosin isoforms. It is found that, by these criteria, at 9 days part of the ventricular conduction system consists of a myocardial ring located around the infundibula of the aorta and truncus pulmonalis. Part of this ring is formed by the retro-aortic root branch. The ring continues via the septal branch into the atrioventricular bundle and its branches, that all express both myosin isoforms. The retro-aortic root branch could be traced back as a part of the myocardial wall of the truncus arteriosus at the 4 days embryonic stage. At the 16th day of development, the septal branch, atrioventricular bundle and left and right bundle branches no longer express the atrial isomyosin, but two bundles originating from the septal branch still express both isomyosins, one being the retro-aortic root branch, the other being only immunologically recognizable and directed to the ventral side of the truncus pulmonalis; this latter we call the pulmonary root branch. Both bundles are remnants of the myocardial ring.

Myosin light chain subunits from adult human atria and ventricle were characterized by two-dimensional gel electrophoresis. Atrial (ALC-1 and ALC-2) differed from ventricular (VLC-1 and VLC-2) light chains. Foetal (18--21 week) ventricle contained VLC-1 plus a foetal light chain (FLC-1) which could not be distinguished from adult ALC-1. Myosin FLC-1 was gradually lost from the ventricle and replaced by VLC-1 during foetal development and in the immediate postnatal period.

We measured the effect of a constant infusion of rat atrial extract on the glomerular filtration rate (GFR), renal plasma flow (RPF), and plasma renin concentration (PRC) of bioassay rats. The infusion rate of the atrial extract was 0.038 ml/min, which represented 1.25 mg of homogenized atrial tissue/min. To ensure that dead space was cleared, clearance measurements during the atrial extract infusion were not begun until urine flow had increased and 300 microliter of urine had been excreted. In the first series of rats, control GFR was 0.69 +/- 0.05, increased to 1.04 +/- 0.06 during infusion of atrial extract, and then decreased to 0.72 +/- 0.08 ml X min-1 X 100 g-1 during the recovery period. In a second series, RPF was also measured. GFR increased from 0.92 +/- 0.02 to 1.15 +/- 0.05 ml X min-1 X 100 g-1, while RPF was unchanged. In both series, the increase in GFR was statistically significant. Constant infusion of atrial extracts had no significant effect on PRC. These studies provide evidence that an atrial factor can cause a large increase in GFR, which may contribute to the natriuretic effect of atrial extracts.

The left ventricular end-systolic pressure-volume relationship is a load-insensitive measure of left ventricular performance. The relationship at end-systole between left ventricular pressure and dimension is more easily obtained, but the conflicting results of previous studies make it unclear if it has the same properties as the left ventricular end-systolic pressure-volume relationship. To address this issue, 11 dogs were instrumented to measure left ventricular pressure and three orthogonal left ventricular dimensions. Left ventricular pressure and dimensions were varied by use of caval occlusion. Left ventricular volume was calculated as an ellipsoid. The left ventricular end-systolic pressure-volume relationship and each of the three end-systolic pressure-dimension relations were described by straight lines (r = .97 +/- .02, mean +/- SD). In six animals, dobutamine produced similar significant increases (p less than .01) in the slope of the end-systolic pressure-volume relationship (244 +/- 61% of control), the end-systolic pressure-anterior-posterior dimension relationship (248 +/- 89%), the end-systolic pressure--septal-lateral dimension relationship (211 +/- 95%), and the end-systolic pressure-basal-apical dimension relationship (210 +/- 85%). The intercepts at zero pressure were relatively unchanged by dobutamine. In contrast, occlusion of the distal left anterior descending coronary artery in five animals produced a rightward shift of the left ventricular end-systolic pressure-volume relationship and the pressure--basal-apical dimension relationship, while the pressure--anterior-posterior dimension and pressure--septal-lateral dimension relationships were relatively unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

Using the recipient's human heart removed at cardiac transplantation, the distribution of digoxin at both the cellular and subcellular level has been studied. In the presence of diffuse histological myocardial abnormalities tissue digoxin is decreased, but the subcellular distribution, presumably reflecting binding to a possible receptor site, is uniform. When the histological abnormality is focal then digoxin distribution is uniform.These results suggest that in the presence of myocardial ischaemia plasma digoxin concentrations may not reflect total myocardial levels accurately.

Tissue levels of atrial natriuretic polypeptide (ANP) and ANP messenger RNA (mRNA) in the atrium and ventricle were measured simultaneously in spontaneously hypertensive rats (SHR) and its substrain, SHR-stroke prone (SHRSP), and these levels were compared with those in control Wistar-Kyoto rats (WKY). At 27 weeks of age with established hypertension and ventricular hypertrophy, ANPmRNA levels in ventricles from SHR and SHRSP were markedly increased, and total contents of ventricular ANPmRNA in SHR and SHRSP were approximately 50% and 250%, respectively, of the corresponding atrial contents. However, levels and total contents of atrial ANPmRNA in SHR and SHRSP were similar to those of WKY, and the total content of ventricular ANPmRNA in WKY was only 6% of the content of atrial ANPmRNA. ANP concentrations in ventricles of SHR and SHRSP were increased in association with the augmentation of ANPmRNA levels. During the prehypertensive stage at 6 weeks of age, slight increases in levels and total contents of ANPmRNA and ANP in the ventricle were observed only in SHRSP. These results demonstrate that the expression of the ANP gene is markedly augmented in ventricles of SHR and SHRSP, especially of SHRSP, at the stage of established hypertension and ventricular hypertrophy, and they also suggest that these genetically hypertensive rats are one of the best animal models to investigate the biosynthesis, storage, and secretion of ventricular ANP.

The concentration of myocardial cyclic AMP was measured in 9 dogs by radioimmunoassay after the administration of aminophylline. Fourteen dogs served as control. The concentration of cyclic AMP in the left ventricle was the highest and the lowest value was obtained in the right atrium in the control dogs. Ventricular fibrillations were induced immediately after the injection of 30 mg/Kg aminophylline in 3 dogs out of 9. The concentration of the left ventricular cyclic AMP in 6 dogs which tolerated aminophylline was significantly elevated compared with that of the control dogs (p less than 0.05). The left ventricular cyclic AMP in 3 dogs with ventricular fibrillation was significantly higher compared with that in the aminophylline tolerated dogs with non-fibrillating hearts (p less than 0.01). These results showed that the concentration of cyclic AMP was elevated in the fibrillating heart.

1. Gel electrophoretic analysis of structural proteins extracted from myocardial tissues in the presence of sodium dodecylsulfate (SDS) is applicable to study the relative amount of structural proteins from less than 1 Gm of heart tissue. 2. The compositions of structural proteins of the right and left atria and ventricles of the normal canine heart were identical and similar to those of skeletal muscle. 3. The compositions of structural proteins of the atrium and ventricle of the normal human heart were also identical.

A high intravenous dose of norepinephrine (4 micrograms/kg/min for 60 minutes) to New Zealand Red rabbits produced patchy subendocardial damage (estimated stereologically in frozen sections) of about 5% of the heart volume 2 days after application. The damaged areas showed loss of staining for alkaline phosphatase, an enzyme present in normal capillary endothelium. Heart performance (cardiac output index, cardiac work [i.e., cardiac output X mean blood pressure], and dP/dtmax) were significantly lower than in control hearts. Capillary density distribution estimated in nondamaged areas of the left ventricular free wall was inhomogeneous favoring subepicardial regions, while homogeneous transmural distribution was found in control hearts. Bradycardial pacing (reduction of heart rate to 50% of normal) performed for 3-4 weeks prior to norepinephrine administration showed a protective effect against catecholamine damage manifested in a smaller extent of necrosis, in the maintenance of homogeneous transmural capillary distribution in nondamaged areas, and, most importantly, in the maintenance of normal cardiac pump performance at rest and during maximal work in response to acutely administered norepinephrine.

Serum, right atrial myocardium and skeletal muscle collected from 32 adult patients undergoing open heart surgery were analyzed for digoxin by radioimmunoassay. Preoperatively 20 patients were in sinus rhythm, but not in patients with atrial fibrillation, there was a highly significant correlation between digoxin concentration in serum and right atrial myocardium, in skeletal muscle and right atrial myocardium, and in serum and skeletal muscle. The means and variances of the ratios right atrial myocardium/serum and right atrial myocardium skeletal muscle were significantly higher in patients with atrial fibrillation than in those with sinus rhythm. This, plus the lack of difference in ratios skeletal muscle serum between these groups of patients, indicate increased right atrial digoxin binding in atrial fibrillation in man. This conclusion is further supported by the finding of similar or higher digoxin concentration in right atrial myocardium than in left ventricular myocardium in atrial fibrillation (6 patients), and a lower digoxin concentration in right atrial myocardium than in left ventricular myocardium in sinus rhythm (3 patients).

A comparative study of vertebrate ventricle tropomyosin has been carried out from the viewpoint of molecular evolution. The ventricles containing one-component tropomyosin were generally known, and in this paper those containing two components were also found in 8 species among mammals, reptiles, amphibia, and fish, but not among birds. The two components were concluded to be authentic tropomyosin and not artifacts since they showed lower electrophoretic mobilities in the presence of urea, and they were precipitated at pH 4.5 and bound to F-actin. Studies on cysteine contents and cyanogen bromide cleavage peptide patterns revealed that the characteristics of the two tropomyosin components from pig, turtle, amphibia and carp ventricles varied increasingly in that order from typical alpha- and beta-characteristics as seen in rabbit skeletal muscle tropomyosin. The single component of chicken ventricle tropomyosin showed alpha component characteristics in its electrophoretic mobility and cysteine content, and beta component characteristics in cyanogen bromide cleavage peptide pattern. The two components of carp ventricle tropomyosin seemed to be the most primitive, having two cysteine residues per molecule and a cyanogen bromide cleavage peptide pattern different from those of the two components of rabbit skeletal muscle.

The performance of the heart depends on the concentrations of free calcium ions in the cytoplasm of the myocytes. However, direct evidence for changes in free Ca concentration in physiological events during response to drugs and in pathogenesis has been difficult to obtain because of technical problems in measuring free Ca at 10(-7) M in cells with a volume of only a few picolitres. Here we describe measurements made with the Ca-sensitive photoprotein aequorin in single ventricular myocytes isolated from rat heart. We have detected signals from resting and contracting cells, and from cells exposed to media of altered ionic composition (raised K, lowered Na), ouabain and metabolic inhibitors. We report that free Ca in metabolically-poisoned myocytes is remarkably stable and that severe injury to the cell occurs before the free Ca concentration rises above 1-3 X 10(-7) M, hence cell damage seems to be a cause, not a consequence, of a rise in free Ca. The technique used here should help to resolve many uncertainties regarding free Ca in heart function, and should be particularly valuable for investigating the role of free Ca in ischaemic pathogenesis.

The myoglobin content in the hearts of several fishes is positively correlated with the ecological physiology of the species. In the tuna heart, where the highest myoglobin values are found, the logarithmic relationship between myoglobin content and body weight is reported.

Two antigenically distinct types of myosin heavy chain, referred to as alpha and beta, have been identified in autoptic and bioptic specimens of human heart using specific antimyosin antibodies. By immunofluorescence heavy chain alpha was present in all atrial myocytes and in a variable number of ventricular myocytes. Heavy chain beta was present in all ventricular myocytes and in a number of atrial myocytes. Ventricular hypertrophy in patients with aortic stenosis, systemic hypertension or tetralogy of Fallot was characterized by an almost complete absence of fibres reactive with anti-alpha. A striking decrease in alpha chain reactivity and a parallel increase in beta chain reactivity was apparent in the hypertrophied left atria of patients with mitral stenosis. To quantify these myosin changes a novel procedure was developed whereby myosin was extracted from single cryosections serial to those processed for immunofluorescence and the relative amount of alpha and beta heavy chain was determined by enzyme immunoassay. Heavy chain alpha was less than 5% in most normal ventricular specimens and disappeared completely under the effect of pressure overload. On the other hand heavy chain beta was generally undetectable in the left atrial myocardium but increased up to 90% in biopsies of hypertrophied atria.

To determine the presence and distribution of cardiac myosin isozymes in the human conduction system, we performed an immunohistochemical study using monoclonal antibodies CMA19 and HMC14, which are specific for myosin heavy chains of human atrial type (alpha-type) and ventricular type (beta-type), respectively. Serial frozen sections of human hearts were obtained from autopsy samples and examined by indirect immunofluorescence. Alpha-type was found in all myofibers of sinus node and atrio-ventricular node, and in 55.2 +/- 10.2% (mean +/- SD, n = 5) of the myofibers of ventricular conduction tissue, which consists of the bundle of His, bundle branches, and the Purkinje network. In contrast, beta-type was found in all myofibers of the atrio-ventricular node and ventricular conduction tissue, whereas almost all myofibers of the sinus node were unlabeled by HMC14. Although the number of ventricular myofibers labeled by CMA19 was small, the labeled myofibers were more numerous in the subepicardial region than in the subendocardial region. These findings show that the gene coding for alpha-type is expressed predominantly in specialized myocardium compared with the adjacent ordinary working myocardium.

Cells from the neural crest over occipital somites migrate to the heart, where they give rise to parasympathetic postganglionic neurons as well as ectomesenchymal elements which contribute to conotruncal septation. With a microcautery needle, the neural crest over occipital somites was ablated bilaterally in chicken embryos at an early stage of development. Histological examination on incubation day 15 revealed conotruncal malformations, involving malformation or absence of the conotruncal septum in all embryos. Two peaks of embryo mortality were observed. One peak (incubation days 6-8) occurred at the same time as conotruncal septal closure; the second peak (incubation days 11-13) was concurrent with the onset of functional parasympathetic innervation. A disruption of parasympathetic innervation was indicated by: (1) a decrease in acetylcholinesterase staining, (2) a decrease (27%) in the number of ganglion cells in the conotruncus, (3) decreases in the acetylcholine content of atrium (31%) and ventricle (39%), and (4) a decrease (21%) in muscarinic acetylcholine receptor density on incubation day 15. Radiolabeled ligand-binding studies revealed no change in the affinity of cardiac muscarinic receptors for [3H]methylscopolamine (KD = 0.17-0.21 nM). Agonist-binding affinity and sensitivity to guanine nucleotides were similarly unaffected. The reasons for the limited extent of the parasympathetic lesion are unclear, but may involve recruitment of precursor cells from other regions of the neural crest, partial regeneration of the neural crest following surgical removal, or an alteration in the contribution of incoming sympathetic or preganglionic parasympathetic elements. No such plasticity was associated with neural crest contributions to the structural development of the conotruncus. Malformations were observed in all lesioned embryos.

Comparisons were made between myosins isolated from the right and left ventricles and the atria of normal human hearts. Parameters examined included electrophoretic mobilities of native molecules, K+ and Ca2+ dependent enzymatic activities, light chain composition, peptide patterns from partial proteolytic digests of entire heavy chains or rods, and maps of complete digests of specific 21 and 25 kilodalton heavy chain fragments. Human ventricular and atrial myosins differ in all parameters except in the charge of molecules. Structural differences between cardiac myosins derived from the two sources were apparent in both the head and tail portions of the heavy chains. With respect to the above parameters no differences were found between myosins from left and right human ventricles.

The inotropic responsiveness of the developing myocardium to dopamine and isoproterenol was evaluated using isolated, perfused ventricles and atrial strips from puppies ages 15 hr to 33 days. Responses were compared to those in adult animals. The maximum percentage of increase of left ventricular dF/dt increased from 12 +/- 5 (mean +/- SEM) at 0-7 days (n = 6) to 100 +/- 40 at 21-33 days (n = 3) of postnatal age. At 7-14 days (n = 4) and 15-20 days (n = 5) of age the maximum percentage of increase of left ventricular dF/dt was 28 +/- 10 and 39 +/- 17, respectively. Puppy ventricle responded to isoproterenol at all ages equally (maximum percentage increase of left ventricular dF/dt = 46 +/- 13). Atrial muscle strips from puppies, ages 15 hr to 35 days (n = 22), and adult dogs (n = 19) demonstrated equal responsiveness to dopamine as well as to isoproterenol. The maximum percentage of increase of dF/dt was 117 +/- 18 with dopamine. Maximum percentage of increase of dF/dt with dopamine after propranolol (10(-7) M) was 52 +/- 18. Haloperidol (1.10(-7)-2.10(-6) M) did not alter responsiveness of atria to dopamine.

In order to evaluate more directly the implications of the sympatho-adrenal system in one-kidney, one clip hypertension (1K1C), we studied adrenal catecholamine synthesis after a bolus injection of 3H-tyrosine, tissue norepinephrine and dopamine concentrations, as well as the urinary excretions of norepinephrine, epinephrine, dopamine and those of the major dopamine metabolites, dihydroxphenylacetic acid (DOPAC) and homovanillic acid (HVA) in 1K1C and control uninephrectomized rats. When compared with controls, the hypertensive rats had a markedly enhanced formation of adrenal 3H-norepinephrine and 3H-epinephrine, higher urinary norepinephrine and epinephrine excretions but lower heart and kidney content of norepinephrine and dopamine as well as decreased urinary excretions of the main dopamine metabolites, DOPAC and HVA. These data suggest an increased norepinephrine and epinephrine synthesis in 1K1C hypertensive rats associated with dopamine synthesis, which is normal but probably disproportionally low relative to the synthesis of norepinephrine and epinephrine. This abnormality may be an important pathogenetic factor in this model of experimental hypertension.

Hybridomas were prepared from mice immunized with myosin from the enlarged left ventricle of a 53-year-old female bearing an obstructive cardiomyopathy. With several different experimental approaches using anti-myosin antibodies, at least two subpopulations of atrial and at least two subpopulations of ventricular myosin were detected, characterized and located in normal human hearts. The human atrium and human ventricle each contained small zones of myosin variation which were scattered, but probably not randomly distributed, within a large area of myocardium whose cellular distribution of myosin was constant. Recent applications of the same approach to the study of the regional variations of the different myosin forms within two pathological human hearts are discussed.

Left ventricular collagen of various mammals (cat, cow, dog, pig, and rat) was successively extracted with neutral salt, and dilute acid solutions, and limited pepsin digestion. The distribution of the various types of collagen molecules in pepsin-solubilized ventricular collagen was analyzed electrophoretically on SDS-polyacrylamide gels in the presence of 3.6 M urea. Yields of dilute-acid-soluble collagen were only 0.4 to 0.6% of the total ventricular collagen, and less than 0.1% with neutral salt solution. Approx. 55-90% of the total collagen was extracted by limited pepsin digestion. Disc patterns of pepsin-soluble collagen revealed the presence of dimeric and trimeric components, as well as higher-molecular-weight aggregates in all samples of nonreduced and reduced ventricular collagen. Taken together, these findings suggest the presence of an extensive interchain and intermolecular cross-linking network in left ventricular collagen. Comparison of electrophoretical disc gel patterns of reduced and nonreduced pepsin-solubilized collagen indicated that left ventricular collagen is heterogenous in nature, consisting of a mixture of type I and type III collagen. It was evident that primarily type I components occur in ventricular collagen. The components of type III collagen molecules occurred in all investigated left ventricles in varying and consistently appreciably lower amounts. The proportions of type III and type I collagen vary in left ventricular tissue of different species.

We developed a head-space method for the determination of blood cyanide by gas chromatography with electron-capture detection. In this technique, a reaction pre-column, packed with chloramine-T, was used for the conversion of hydrogen cyanide into cyanogen chloride. Since the reaction pre-column eliminated the necessity for trapping hydrogen cyanide from the biological samples, blood cyanide was quickly analysed by acidification only. The reaction pre-column was durable for at least several months. The calibration curve gave good linearity when dichloromethane was used as the internal standard, and the lower detection limit taken from this plot was ca. 0.05 micrograms/ml. The relative standard deviation of spiked blood samples was in the range 0.6-3.9%. We determined blood cyanide levels at autopsy in victims who had died from fire using this method. A significantly higher cyanide content was detected in the left ventricular blood than in the right. There was a positive correlation between blood cyanide and carboxylhaemoglobin contents. This simple and sensitive technique could be very useful for the determination of cyanide in various samples.

We have isolated essentially full-length cDNA clones for atrial (ALC1) and ventricular (VLC1) myosin alkali light chains from a human fetal heart cDNA library. Comparison of overall nucleotide sequences of ALC1 and VLC1 cDNA clones has revealed that, while these two inserts show significant DNA sequence homology (78.4%) with respect to their coding regions, the 5'- and 3'-untranslated regions are highly divergent. Our statistical analysis suggests that human ALC1 and VLC1 diverged approximately 300 million years ago, during the time of separation of birds and mammals. RNA blot analysis shows that ALC1 mRNA is expressed in fetal ventricular and fetal skeletal muscles as well as fetal and adult atrial muscles and VLC1 mRNA is expressed in adult slow skeletal muscle as well as fetal and adult ventricular muscles. Southern blot analysis indicates that each protein is encoded by a single gene. Finally, we show that VLC1 mRNA is induced in pressure-overloaded human atrium.

Membrane-bound receptor or enzyme distribution between cell surface and cell interior can be determined using the non-ionic detergent digitonin. A solid-phase radioimmunoassay using myocardial cells from newborn rats was performed to screen hybridoma culture supernatants and the cells were rendered permeable with increasing concentrations of digitonin (0-0.1%). This was achieved in 5 min at 37 degrees C and did not require the continuous presence of detergent. A characteristic amount of cytoplasmic protein (approximately equal to 45%) was released with subunit molecular weights of up to 200,000. This allowed exogenous molecules such as immunoglobulin G to gain access to the intracellular targets. The binding to rat myocardial cells of 36 monoclonal antibodies was examined by this procedure. The binding assays were carried out for 30 min at 37 degrees C using cells previously treated for 10 min with 0.05% of digitonin. This appears to be a simple and rapid method of screening and selecting the hybridoma culture supernatants.

Although alterations in cardiac reflex activity, as well as in cardiac norepinephrine stores, have been shown following thoracic operations, the physiological relationship between these alterations has not been investigated. Cardiac norepinephrine stores were examined in 17 normal dogs, and in 16 dogs 1-6 wk after a right thoracotomy. The heart rate response to induced arterial hypotension (mean decrease 17-20 mmHg) prior to and following surgery was also examined in 10 dogs. A significant depression in right atrial norepinephrine stores from normal levels of 1.95 +/- 0.13 mug/g to 1.30 +/- 0.25 mug/g (33%) (P less than 0.05) was observed during the first wk following surgery. During the same period the heart rate response to a fall of 17-20 mmHg systolic arterial pressure was clearly reduced from 52.8 +/- 6.9 beats/min to 17.0 +/- 4.8 beats/min (67.8%; P less than 0.05). Right atrial norepinephrine stores at the time of the initial operation and when reflex responses were most markedly depressed demonstrated that the decrease in norepinephrine stores was paralleled by attenuation of the chronotropic response to hypotension.

The need for ventricular venting with hypothermic cardioplegic arrest is controversial. We report an evaluation of the need for left ventricular venting in a canine model that closely simulates conditions during routine coronary artery bypass grafting (CABG). Thirty-five dogs were placed on cardiopulmonary bypass for 60 minutes of hypothermic cardioplegic arrest (18 vented, 17 nonvented) and then reperfused for 30 minutes. Myocardial temperature and left atrial pressure (LAP) were recorded continuously. Before and 30 minutes after hypothermic cardioplegic arrest, left ventricular function curves were generated (six vented, six nonvented), and biopsy specimens of the left ventricle were taken for adenosine triphosphate (ATP) determinations (11 vented, 10 nonvented) and semiquantitative grading of mitochondrial ultrastructure (six vented, six nonvented). LAP in nonvented dogs was 7.4 mm Hg during hypothermic cardioplegic arrest and 5.0 mm Hg during reperfusion. Temperature during hypothermic cardioplegic arrest was 12.3 degrees C in vented dogs and 11.3 degrees C in nonvented dogs (p = 0.5). There were no differences in left ventricular function or preservation of mitochondrial ultrastructure between vented and nonvented dogs. ATP after hypothermic cardioplegic arrest was 96.6% of control (4.30 microM/gm) in vented dogs and 94.6% (4.37 microM/gm) in nonvented dogs (p = 0.7). The absence of left ventricular venting did not lead to ventricular distention or more rapid rewarming. These data in vented dogs and nonvented dogs strongly support the belief that left ventricular venting is not necessary during routine CABG.

We describe a method for the complete solubilization and quantitative analysis of individual myofibrillar proteins in whole tissue homogenates of ventricular myocardium using gradient dodecyl sulfate polyacrylamide gel electrophoresis and staining with 125I-labeled Coomassie brilliant blue. The procedure allows for the simultaneous quantification of myosin heavy chain, myosin light chain, phosphorylatable myosin light chain and actin from as little as 50 mg of tissue. Within-assay and between-assay variations range from 8.0% to 12.6% for each protein subunit. The method was applied to the determination of the subunit stoichiometry of purified myosin, and to the measurement of myosin and actin concentrations in the neonatal and adult rabbit heart. Furthermore, we provide quantitative biochemical evidence for the existence of large molar excesses of myosin light chains in tissue homogenates of both neonatal and adult rabbit ventricular myocardium.

The effect of age on the density and the affinity of beta adrenergic receptors was determined in the hearts of Fischer 344 rats at three ages, 6, 12, and 24 months old. The binding of the beta adrenergic antagonist 125I-iodohydroxybenzylpindolol (IHYP), was used to quantitate and characterize cardiac beta adrenergic receptors. The maximal number of binding sites (Bmax = F moles/mg of protein) were 26.3 +/- 2.5, 25.4 +/- 0.99, and 24.5 +/- 2.4 and the dissociation constants (Kd = nM) were 0.166 +/- 0.014, 0.126 +/- 0.006, and 0.135 +/- 0.015 for 6, 12, and 24 months old animals, respectively. There were no significant differences among the three ages. These results support the contention that neither beta adrenergic receptor density or affinity changes with age in the ventricles of the rat heart.

Atrial natriuretic peptide (ANP) is a newly discovered peptide hormone present mainly in the atria. We investigated the occurrence and distribution of ANP immunoreactivity in the myocardiocytes of the ventricles of spontaneously hypertensive rats by use of immunocytochemistry at both light and electron microscopic level. ANP immunoreactivity was found in the specific granules in the cytoplasm of the cardiocytes in the subendocardium and the myocardium of the ventricles, as well as in the atria. The specific granules found in the ventricles of hypertensive rats were similar in size, shape, and ANP immunoreactive content to those in the atria. The abundance of ANP immunoreactivity in the left ventricle is greater than that in the right, and appears to increase with increasing severity of hypertension. Conversely, the overall content of ANP in the atria of hypertensive rats was decreased when compared with that in age-matched normotensive rats. The present findings indicate that ventricles may become a major source for ANP synthesis and release during hypertension, and may play important roles in cardiac endocrine pathology and cardiac hypertrophy.

Estimates of the collagen concentration in human ventricles have been made from measurements of the hydroxyproline concentration. In the normal heart the concentration of collagen was higher in the right ventricle than in the left ventricle. Age had no effect on the ventricular concentration of collagen. Hypertrophy in the absence of a valvar lesion was not associated with an increased concentration of collagen but, owing to the increased size of the ventricle, there was an increase in the estimated total mass of ventricular collagen. The concentration of collagen in the left ventricle of patients with aortic stenosis was higher than normal. Ventricular hypertrophy seems to be accompanied by an increase in the total mass of collagen whatever the cause. Whether the concentration changes or not depends on the proportion in which the mass of collagen increases relative to the mass of muscle cells.

We examined the effects of various coronary vasodilator drugs, papaverine, dipyridamole, isosorbide dinitrate, amyl nitrite, nitroglycerin, diltiazem, and nifedipine, on cyclic nucleotides of the coronary artery and left ventricular muscle of anesthetized dogs at maximum coronary blood flow after the administration of each agents. Only papaverine and dipyridamole significantly increased the concentration of c-AMP in the coronary artery. Nitroglycerin and siosorbide dinitrate did not significantly change the concentration of c-AMP but rather increased the concentration of c-GMP. Coronary vasodilator drugs were divided into three groups in association with the relationship of cyclic nucleotides in the coronary artery. Group I, including papaverine, dipyridamole, and amyl nitrite, increased the concentration of c-AMP and the ratio of c-AMP to c-GMP. Group II, including nitroglycerin and isosorbide dinitrate, incrased the concentration of c-GMP and decreased the ratio of c-AMP to c-GMP. Group III, including nifedipine and diltiazem, had no effect on the cyclic nucleotides. Group I drugs also increased the concentration of c-AMP in the left ventricular muscle and so group I drugs may predispose the ischemic heart to develop ventricular arrhythmias. It seems that the most useful coronary vasodilator is no effect on the c-AMP in the ventricular muscle and group II and group III drugs are more useful coronary vasodilator drugs than group I drugs.

Antibodies were produced against myosins isolated from the left atrial myocardium (anti-bAm) and the left ventricular myocardium (anti-bVm) of the bovine heart. Cross-reactive antibodies were removed by cross-absorption. Absorbed anti-bAm and anti-bVm were specific for the myosin heavy chains when tested by enzyme immunoassay combined with SDS gel electrophoresis. Indirect immunofluorescence was used to determine the reactivity of atrial muscle fibers to the two antibodies. Three populations of atrial muscle fibers were distinguished in the bovine heart: (a) fibers reactive with anti-bAm and unreactive with anti-bVm, like most fibers in the left atrium; (b) fibers reactive with both antibodies, especially numerous in the right atrium; (c) fibers reactive with anti-bVm and unreactive with anti-bAm, present only in the interatrial septum and in specific regions of the right atrium, such as the crista terminalis. These findings can be accounted for by postulating the existence of two distinct types of atrial myosin heavy chains, one of which is antigenically related to ventricular myosin. The tendency for fibers labeled by anti-bVm to occur frequently in bundles and their preferential distribution in the crista terminalis, namely along one of the main conduction pathways between the sinus node and the atrioventricular node, and in the interatrial septum, where different internodal tracts are known to converge, suggests that these fibers may be specialized for faster conduction.