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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)

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.

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.

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.

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)

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.

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 have prepared monoclonal antibodies specific for either atrial or ventricular myosin and defined the isomyosin composition of myocardium in normal and overloaded human hearts. In the atrial myocardium, normal isozymic pattern was V1 dominant which converted to being V3 dominant in an overloaded condition. In contrast, normal isomyosin pattern of the ventricular myocardium was exclusively V3 dominant, and only a small change in the proportion of isomyosin was observed in an overloaded condition. From this, we conclude that isozymic changes in cardiac myosin could occur in the human heart to meet increased work induced by cardiac overload. However, the physiological importance of these isomyosin redistributions in human myocardium seems to be much greater in the atrium than in the ventricle, since larger amounts of V1 isomyosin which could be transformed to V3 isomyosin were present in the atrial myocardium.

To obtain further evidence concerning the intracellular action of ouabain, we observed the effect of this compound on contractures evoked by rapid cooling in the presence of caffeine (rapid cooling caffeine contracture; RCCC), in cardiac muscles under conditions of a Ca deprived medium. The experiments were carried out at 20 degrees C using cat papillary muscles and frog ventricle strips, with the exception of cooling (2 degrees C). The muscles were first immersed in normal solution, electrically driven, then immersed in 1 mM EDTA solution for 6 min. The strips were then immersed for 10 min in a caffeine solution prepared by eluting a no-Ca solution containing 50 mM caffeine through Dowex A-1, Ca-chelating resin. Finally, the caffeine solution was exchanged with fresh caffeine solution of 2 degrees C to evoke to RCCC. Ouabain (1 X 10(-7)--1 X 10(-5) M) markedly potentiated RCCC. An ouabain-induced increase of RCCC did not appear in the resting strips unless the tissues were electrically stimulated. 3H-ouabain occupied a considerable cellular space (0.55) at the appearance of the ouabain potentiation of RCCC (14C-inulin space; 0.20). The appearance of the ouabain potentiation of RCCC was independent of changes in 22Na, Ca2+ and ATP contents in the strips. A possible mechanism of the potentiating effect of ouabain on contraction is discussed.

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.

The myosin light chain complement and proteolytic peptide patterns of myosin heavy chains were studied by two-dimensional and one-dimensional electrophoretic techniques respectively, in a total of 57 samples from ventricular and atrial tissues of normal and hypertrophied human hearts. Hypertrophies were classified haemodynamically as due to pressure-overload and volume-overload. In addition to the occurrence of ventricular light chains in hypertrophied atria we also observed the atrial light chain-1 (ALC-1) in hypertrophied ventricular tissues. On average over 6% of total light-chain-1 comprised ALC-1 in pressure-overloaded ventricles and around 3% in volume-overloaded ventricles. In single cases of pressure-overload ALC-1 amounted up to over 20% of total light chain-1. With regard to the myosin heavy chains limited digestion by two different proteinases produced over 200 clearly resoluble peptides. The absence of any detectable differences in the peptide patterns between myosin heavy chains from normal and hypertrophic tissues of left or right ventricle is in line with the findings of J. J. Schier and R. S. Adelstein (J Clin Invest 1982; 69: 816-825). In atrial tissues however, reproducible qualitative differences in the peptide patterns indicated that during hypertrophy a different type of myosin heavy chains becomes expressed. No differences were seen between the myosin heavy chains from normal left and right atria.

Somatostatin has been shown to have negative inotropic and chronotopic effects and to restore sinus rhythm in some cases of cardiac arrhythmia. Using acid extracts, regions of human heart were examined by radioimmunoassay to determine their somatostatin content. Mean (SD) concentrations of 4.1 (0.8) pmol/g and 2.9 (0.8) pmol/g were found in atrioventricular node and right atria respectively and were significantly higher than in other heart regions. Using fresh heart tissue from guinea pigs, somatostatin was localised to cardiac nerves by immunocytochemistry. Nerves containing somatostatin were most abundant in the atria, where the concentrations measured by radioimmunoassay were 7.6 (1.0) and 2.6 (0.4) pmol/g for right and left atria respectively. Somatostatin contained in cardiac nerves may have a physiological role in the cardiac conduction system.

A micro-analysis was designed for determining the levels of coenzyme Q10 (CoQ10) in specimens of ca. 500 nanograms of myocardial tissues. The prime steps included acetone extraction, purification by thin-layer chromatography, and HPLC. CoQ11 was the internal standard. This methodology was successful for human endomyocardial biopsies from cardiac patients before and after therapy with CoQ10 and has now been used for canine and bovine tissues. The mean canine CoQ10 level from six specimens from the left ventricle (l.v.) of a single animal is 0.99 +/- 0.06 micrograms/mg/d.w. The mean levels of the tissues from nine animals is 1.04 +/- 0.17 (l.v.) and 1.11 +/- 0.16 (r.v.). The mean bovine level from seven animals was 0.48 +/- 0.12 (l.v.) and 0.68 +/- 0.06 (r.v.).

Although high blood transfusion regimens have improved the life expectancy of the patient with Thalassemia Major, cardiac failure and arrhythmias remain a cause of early death. It is not certain whether the massive myocardial iron deposition found in such patients is preventable by intensive chelation therapy. This study evaluates endomyocardial biopsy as a method of assessing myocardial iron deposition. Of four patients with clinical and biochemical evidence of severe haemochromatosis, only one had a myocardial iron content comparable to that found in severe haemochromatotic myocardium. The one patient with cardiac failure had an endomyocardial iron content within the normal range. Studies of the iron distribution in haemochromatotic myocardium demonstrate that the subendocardial myocardium contains only half the iron content of the subepicardial layer, and there is a large sampling variation. It is concluded that catheter endomyocardial biopsy is an insensitive method of determining early myocardial deposition because of the location of iron and the variability of the sampling. Studies of the nature of the myocardial iron protein with CM32 cation exchange resin chromatography show that there is a large increase in the haemosiderin: ferritin ratio (5:1) in iron overload myocardium as compared with the normal heart (2:1). Similar results have been observed in the liver with iron overload, where the increase in hepatic haemosiderin was associated with greater lysosomal fragility. It is possible that myocardial cell damage may also occur by the rupture of iron engorged lysosomes.

Histochemical and ultrastructural aspects of the heart were investigated in an adolescent with fatal congestive heart failure resulting from exogenous hemochromatosis. Extensive iron deposits were found in all four chambers, papillary muscles, and the conduction system. These deposits were most prominent over the outer third of the left ventricular myocardium, with no significant difference between deposits in the middle and inner thirds. Quantitative analysis of iron from different chambers and all zones of the left ventricular myocardium confirmed the aforementioned pattern of iron distribution. Iron deposits in sinoauricular and atrioventricular nodes were similar to those in the right atrial myocardium. Degenerative changes and fibrosis were minimal. Ultrastructural studies showed that intracytoplasmic iron deposition followed a perinuclear, paranuclear, or diffuse pattern. In addition, some iron was consistently present in the nucleus and mitochondria. It is postulated that the presence of iron in the mitochondria may adversely affect the cellular enzyme system; this could provide a biochemical basis for myocardial dysfunction in patients with acquired iron-storage disease.

1. Protein constituents of cardiac muscles of 23 species were examined by two-dimensional gel electrophoresis in order to find the difference in protein components between atria and ventricles. 2. Protein compositions of atria were similar to those of ventricles, however, differences were found in myosin and some other proteins in most species. 3. A major protein with molecular weights of 12,000-15,000 daltons was distributed only in atria from mammals. 4. The atrioventricular difference suggested that the ventricular tissue was more specialized in mammals than in birds, as compared with the atrial tissue.

Electrophoretic analysis on sodium pyrophosphate gels of myosin light chain 1 (LC-1; 27,000 daltons) from rabbit ventricular heart muscle revealed the presence of two distinct components named LC-1a (10%) and LC-1b (90%). After thyroxine administration, a shift toward LC-1a (45%) was observed. Canine cardiac ventricular light chain 1 (27,000 daltons) had equal amounts of LC-1a' (50%) and LC-1b' (50%), which corresponded to LC-1a and LC-1b of rabbit heart, respectively. However, heterogeneity of light chain 2 (20,000 daltons) was not observed. It is concluded that cardiac ventricular myosin has two heterogeneous 27,000 dalton-light chains and that the proportion of these proteins varies according to the thyroid status and animal species.

Fatty acid composition of human heart phospholipids was determined in 53 specimens of left ventricular myocardium collected during mitral valve replacement. Ages of the subjects (29 males and 24 females) ranged from 14 to 75 years (mean age = 54). Samples were immediately placed in chloroform-methanol 2/1, v/v to which antioxidant was added. Extracted phospholipids were converted to methyl esters which were analyzed by gas liquid chromatography on glass capillary columns. Morphological examination was also performed on 35 out of 53 samples. Age of the patients as well as the morphological state of the organ had no significant effect on major fatty acids in heart phospholipids. No difference by sex was detected. Trans-octadecenoic isomers were detected in all samples but they remained at a low level (0.4% to 1.2% of the total fatty acids).

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.

Using anaesthetised rats we have assessed (1) whether the density of alpha 1 adrenergic receptors increases during coronary artery occlusion, (2) whether any change in density can be associated with the onset of reperfusion induced ventricular fibrillation, and (3) whether alpha 1 blockade with prazosin modifies the incidence of reperfusion induced ventricular fibrillation. The incidence of fibrillation upon reperfusion after 3, 5, 10, 20 and 30 min occlusion was 20, 75, 50, 16 and 10% (n = 10-12 in each group) respectively. alpha 1 Receptor density was measured using [3H]-prazosin in non-ischaemic and ischaemic tissue obtained after 0, 5 and 30 min ischaemia. Receptor density was not significantly altered at the time of maximum incidence of reperfusion induced ventricular fibrillation (5 min occlusion) but did significantly increase in both non-ischaemic and ischaemic tissue after 30 min occlusion, when the incidence of fibrillation upon reperfusion was very low (8%). At this time the values were 17.0(SEM 2.3) and 18.4(0.6)fmol.mg-1 protein in non-ischaemic and ischaemic zones as compared to 10.7(0.6) and 12.8(1.0)fmol.mg-1 protein in sham operated control animals (p less than 0.05 in both cases). Prazosin (0.1 or 1.0 mg.kg-1 body wt intravenously, 5 min prior to coronary occlusion) did not alter the incidence of ventricular fibrillation, ventricular tachycardia or total number of premature ventricular complexes upon reperfusion. We conclude that ischaemia induced changes in alpha 1 receptor density do not parallel changes in vulnerability to reperfusion induced arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular collagen of rats aged 1,4,8, and 24 months, as well as young and adult pigs and beef, was successively extracted with neutral salt and dilute acid solutions and limited pepsin digestion. The distribution of type I and III collagen molecules in pepsin-solubilized collagen was analyzed with sodium dodecyl sulphate polyacrylamide gel electrophoresis in the presence of 3.6 M urea, under nonreducing and reducing conditions. Yields of dilute-acid-soluble collagen ad neutral-salt-soluble collagen were extremely low (0.3-0.8%, and less than 0.3% of total starting collagen, respectively), indicating the presence of an extensive interchain and intermolecular cross-linking network in left ventricular tissue of young and mature mammals. Comparison of protein patterns in electrophoresis gels indicated that myocardial collagen consists primarily of type I collagen molecules. The components of type III collagen also occurred in all investigated preparations, in varying and consistently lower proportions. The ratio of type III to type I collagen changed during postnatal growth and aging.

The patterns of distribution of histamine and norepinephrine among the 4 chambers of the heart of rats, guinea pigs, and rabbits and among 15 portions of the dog heart were quite similar, except for the coronary ring of the dog, which was disproportionately high in histamine. In whole mouse hearts the separate chambers were not assayed; in the whole heart, the contents of the 2 amines did not correlate. The subcellular distribution of histamine in the rat and guinea pig heart was different from that of norepinephrine. Histamine was mostly associated with mast cell-like granules. Toluidine blue-staining granules of 2 widely different densities were found.

The effect of intraperitoneal noradrenaline injection (2.5 mg/kg body weight) on myocardial levels of cAMP, cHMP, PGE and PGF2 alpha of the left and right ventricles was examined in male Wistar rats. The findings were compared with morphologic changes in the myocardium and sympathetic nerves of both ventricles. Cyclic nucleotides and PGs were measured by RIA, sympathetic nerves, by a fluorescent histochemical technique; myocardial lesions were demonstrated by Lie-staining. A sharp drop was noted in cAMP and PG levels at early stages of the experiment followed by a gradual return to control values. The decrease in cAMP was less marked, and more transient, in the right ventricle. These changes were accompanied with a more pronounced damage to the left ventricle, perhaps due to differences in adrenergic innervation as well as cyclic nucleotides and PG metabolism in the examined compartments of the heart.

To determine the role of the parasympathetic system in the development of essential hypertension, the concentrations of acetylcholine (ACh) as a parasympathetic marker and norepinephrine (NE) as a sympathetic marker were measured simultaneously in the heart of spontaneously hypertensive rats (SHR) at 4, 10 and 27 weeks of age, and in age-matched control Wistar-Kyoto rats (WKY). ACh was measured using a highly sensitive and specific high performance liquid chromatography-electrochemical detection (HPLC-ECD) attached to a newly developed immobilized fixed enzyme column system. NE was measured by conventional HPLC-ECD. The ACh concentration decreased in the order right atrium (RA) greater than left atrium (LA) greater than right ventricle (RV) greater than interventricular septum (IVS) greater than left ventricle (LV) in both SHR and WKY of all age groups, and NE showed an almost identical pattern. The concentration of ACh tended to increase and that of NE to decrease with age in both strains. The concentrations of ACh in the heart were significantly different in the two strains, with the levels being consistently higher in the SHR strain regardless of age, although differences were most significant at 10 weeks. The mean concentrations of NE were higher in SHR than in WKY, but the differences between the two strains were significant only in the RV and IVS. The functional meanings of a given tissue concentration of a neurotransmitter are still controversial. However, the increase in SHR heart ACh concentration, in parallel with the development of hypertension, may reflect the augmented parasympathetic activity counteracting or compensating for the augmented sympathetic drive in the early stage of hypertension.

The concentration of total lipids, free fatty acids and free carnitine in seven different regions of human ventricular myocardium has been studied. Statistically significant differences were found in the concentration of these compounds in the studied regions, with a similar behaviour for free carnitine and free fatty acids (their highest concentrations were found in the lower zones of the left ventricle). The results obtained support the theory of a different metabolic requirement in relation to the intensity of muscular contractile activity.

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.

Myoglobin has been identified in the heart tissue of three species of antarctic icefish, Chaenocephalus aceratus, Pseudochaenichthys georgianus and Chaenodraco wilsoni. Quantitative analysis shows myoglobin concentrations that are substantially lower than other teleost fish. A simple and accurate method for the direct measurement of myoglobin in tissue is described.

In the dog heart-lung preparation the effects of glucose and mannitol induced hyperosmolality were examined on left ventricular water content, ventricular compliance, cardiac performance, and coronary blood flow. Glucose-induced increase of serum osmolality by more than 20% resulted in a decrease of myocardial water content and an increase of left ventricular diastolic stiffness if insulin was absent, but the changes did not develop if it was present. Insulin failed to prevent the alterations if hyperosmolality was induced with the nonmetabolizable sugar, mannitol. Coronary blood flow increased in each type of experiments. It is concluded that diagnostic and clinical treatment with hyperosmotic solutions of nonmetabolizable agents can account for disturbed left ventricular compliance and decreased cardiac performance, as it may occur in hyperosmolar diabetic coma.

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 non-enzymatic method is presented for isolating mitochondria from small-sized human cardiac samples, including ventricular needle biopsies of 15-25 mg of wet weight. Electron microscopy demonstrates that these fractions are rich in structurally well preserved mitochondria. Calcium and magnesium levels of fractions are determined by atomic absorption flame spectroscopy. Comparative analyses are made in similar fractions of the mouse ventricle. Calcium concentrations of mitocondria isolated in the presence of ruthenium red do not differ significantly between the human auricle and ventricle, averaging 61 nmol Ca/mg protein and 68 nmol Ca/mg protein, respectively. Mitochondrial calcium level is lower in the mouse ventricular fractions, averaging 7 nmol Ca/mg protein. Mitochondrial magnesium amounts to slightly less than 60% of the calcium levels in the human heart, while it exceeds the calcium level by more than 100 per cent in the mouse heart. There is no significant difference of mitochondrial calcium between normal auricles, and, auricles of patients with increased right atrial mean pressure and/or volume overload.

Cardiac atria are thought to be the principle source of plasma atrial natriuretic factor (ANF), a potent natriuretic and diuretic peptide. Whether other ANF production sites are recruited in disease states exhibiting elevated plasma ANF levels is not known. Accordingly, in the cardiomyopathic hamster, an animal model of congestive heart failure with high circulating levels of ANF, contribution of ventricular tissue to total cardiac ANF production and storage was investigated. Measurements were made of immunoreactive ANF in plasma and in atrial and ventricular extracts as well as ANF mRNA levels in the atria and ventricles from normal and cardiomyopathic golden Syrian hamsters. Plasma ANF levels were higher in cardiomyopathic than in control animals. The atrial concentration of ANF (per milligram atrial weight) was 50% and 83% lower in moderate and severe congestive heart failure, respectively, when compared with controls, while atrial ANF mRNA content of cardiomyopathic hamsters was not significantly different from normal hamsters. The ventricular concentration of ANF was 3 times and 7 times higher in animals in moderate and severe heart failure when compared with controls. In severe heart failure, ventricular ANF accounted for 23% of total cardiac stores of ANF. Ventricular ANF mRNA levels were 7 times and 13 times higher in hamsters in moderate and severe heart failure as compared with control animals. Therefore, significant increases in both ANF content and ANF mRNA in ventricles of hamsters in moderate to severe heart failure suggest that the ventricle could be an important source of ANF in congestive heart failure.

Microelectrodes filled with neutral carrier selective to Ca2+ were used to measure the free intracellular Ca2+ concentration [( Ca2+]i) in sheep cardiac tissue and frog skeletal muscle. Calibration of the electrodes was performed in the presence of a solution resembling the cationic composition of the cytoplasm. [Ca2+]i at rest in normal physiological saline (20-22 degrees C) was 240 nM in Purkinje fibres, 270 nM in ventricular muscle, and 52 nM in skeletal muscle. In Purkinje fibres, elevation of [Ca2+]o from 1.8 mM to 5.4 mM produced a 1.7-fold increase in [Ca2+]i. Elevation of [Ca2+]o from 1.8 mM to 18 mM induced a 2.6-fold increase in [Ca2+]i. Exposure to Na+-free solution (Li+-substituted) gave rise to elevation of [Ca2+]i by factors of 5.8 and 14 in ventricular muscle and Purkinje fibres, respectively. These latter changes in [Ca2+]i were associated with the development of contractures which reached 34% and 172% of the corresponding twitch tension.

Antiserum specific for human prealbumin (HPA) was studied by indirect immunofluorescence on tissue sections of cardiac ventricles containing senile cardiac amyloid. The pattern of reactivity was identical to that previously reported for an antiserum specific for protein ASc1 (formerly designated ASCA present in these tissues. Anti-HPA failed to react with isolated atrial amyloid (IAA), primary amyloid (A lambda I, A lambda IV, A lambda VI), secondary amyloid (AA), amyloid associated with medullary carcinoma of the thyroid (AEt), pancreatic amyloid associated with adult onset diabetes, cerebral amyloid present in Alzheimer's disease or lichen amyloid. THe reaction of anti-HPA was completely blocked by purified human prealbumin but was not influenced by absorption with purified human albumin or proteins extracted from any amyloid types tested. The anti-HPA reaction was also completely blocked by purified protein ASc1, and the reaction of anti-ASc1 was similarly blocked by purified HPA. These studies suggest that senile cardiac amyloid of the ASc1 type contains prealbumin or a protein antigenically closely related to this molecule.

To elucidate the role of alpha 1- and beta-adrenergic activities in pressure overload hypertrophy, changes of alpha 1- and beta-adrenoceptors were measured by radioligand binding assay, and the preventive effects of alpha 1- and beta-adrenoceptor blockade on cardiac hypertrophy were assessed in guinea pigs after aortic banding. Five days after banding, dry weight of left ventricle had not increased, though wet weight increased due to marked intercellular oedema. In this period, the maximum binding capacity of [3H] prazosin increased to 31.1 (SEM 2.2) fmol.mg-1 from (sham operation) 17.0(2.1) fmol.mg protein-1, p less than 0.01, whereas the maximum binding capacity of [3H]dihydroalprenolol did not increase: 143(16) fmol.mg-1 (banded) v 153(13) fmol.mg-1 (sham). Three weeks after aortic banding, the maximum binding capacity of both ligands increased to 45.6(5.5) fmol.mg-1 and 232(21) fmol.mg-1, respectively, accompanied by a significant increase in left ventricular dry weight, from 0.46(0.02) mg.g-1 (sham) to 0.62(0.08) mg.g-1 (banded), p less than 0.01. Continuous subcutaneous administration of the alpha 1-blocker bunazosin (0.1 mg.kg-1.d-1) significantly attenuated the increase in left ventricular dry weight whereas the beta-blocker propranolol (5 mg.kg-1.d-1) did not: 0.55(0.03) v 0.66(0.04) mg.g-1 respectively, after 3 weeks. These results show that pressure overload elicited an increase in myocardial alpha 1-adrenoceptors before the onset of cardiac hypertrophy, and that an alpha 1-blocker could prevent the development of hypertrophy in the pressure overloaded heart.

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.