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A study of the connection between perturbed heart rate (HR), stroke volume (SV) and dorsal aortic flow during the evolvement period when essential alterations in mass and morphology take place revealed that there is a stage-dependent connection between SV and the perturbed HR percent of intrinsic HR. This stage dependence was not seen when the SV was standardized at intrinsic HR. Intrinsic HR of the preinnervated embryo is similar to the rate that optimizes dorsal aortic flow despite a monotonic HR-dependent difference in SV.

Carbon dioxide modulation of the contractility response of rat aorta to various agonists was examined in tissues with intact or resected endothelium. The presence of an endothelial layer modified the effect of carbon dioxide on the agonist-induced contraction of aortic segments. Eicosanoids are implicated in the mediation of high carbon dioxide partial pressure-induced modulation of aortic responses to two of the three agents tested as cyclooxygenase inhibitors diminished carbon dioxide effects.

A study was conducted to examine horseradish peroxidase's (HRP) permeable influence on spatial site distribution in the normal rabbit aorta. The study employed image analysis and assumed a minute of circulation. The sites, called HRP spots, had a nonuniform distribution which was qualitatively the same across all experimented rabbits. Results show that HRP spot density was highest in the aortic arch, decreases distally, was lowest in the thoracic aorta and increased again in the abdominal aorta. The results validate the influence of hemodynamic and arterial wall factors.

To study the effect of the degree of unsaturation of dietary fatty acids on the production of free radicals and on the vascular smooth muscle tone in rings of the aorta, Sprague-Dawley rats were fed a semipurified diet containing 5% lipids from either corn oil (CO) or menhaden oil (MO) for 8 wk. The MO diet did not change the basal or NADPH-dependent superoxide anion ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]) release. There were no significant differences in phenylephrine-induced contractions between the two groups in intact rings. However, these contractions increased in endothelium-intact aortic rings from the MO group after addition of the nitric oxide ([multiplied by]NO) synthase inhibitor [N.sup.G]-nitro-L-arginine and in endothelium-denuded rings, both indicating a greater endothelial basal [multiplied by]NO production in rats fed with the MO diet. Endothelium-dependent relaxations in response to acetylcholine were more prominent in rings from the MO group. These differences were not due to an increased smooth muscle response to [multiplied by]NO, because relaxations were the same using an exogenous [multiplied by]NO donor. Our results indicate that dietary MO did not modify [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] release by the vessel wall or relaxation due to the cyclooxygenase pathway, but it potentiated endothelial production of [multiplied by]NO. corn oil; polyunsaturated fatty acids; nitric oxide; superoxide anion

The cellular mechanisms that contribute to the acceleration of atherosclerosis in aging populations are poorly understood, although it is hypothesized that changes in the proliferative capacity of vascular smooth muscle cells is contributory. We addressed the relationship among aging, generation of reactive oxygen species (ROS), and proliferation in primary culture smooth muscle cells (SMC) derived from the aortas of young (4 mo old) and aged (16 mo old) mice to understand the phenotypic modulation of these cells as aging occurs. SMC from aged mice had decreased proliferative capacity in response to [micro]-thrombin stimulation, yet generated higher levels of ROS and had constitutively increased mitogen-activated protein kinase activity, in comparison with cells from younger mice. These effects may be explained by dysregulation of cell cycle-associated proteins such as cyclin D1 and p27Kip1 in SMC from aged mice. Increased ROS generation was associated with decreased endogenous antioxidant activity, increased lipid peroxidation, and mitochondrial DNA damage. Accrual of oxidant-induced damage and decreased proliferative capacity in SMC may explain, in part, the age-associated transition to plaque instability in humans with atherosclerosis. atherosclerosis; reactive oxygen species; cell cycle; DNA damage; lipid peroxidation

To explore the molecular mechanisms responsible for the variation in smooth muscle contractile kinetics, the influence of MgATP, MgADP, and inorganic phosphate ([P.sub.i]) on force and shortening velocity in thiophosphorylated 'fast' (taenia coli: maximal shortening velocity [V.sub.max] = 0.11 ML/s) and 'slow' (aorta: [V.sub.max] = 0.015 ML/s) smooth muscle from the guinea pig were compared. [P.sub.i] inhibited active force with minor effects on the [V.sub.max]. In the taenia coli, 20 mM [P.sub.i] inhibited force by 25%. In the aorta, the effect was markedly less ([is less than] 10%), suggesting differences between fast and slow smooth muscles in the binding of [P.sub.i] or in the relative population of [P.sub.i] binding states during cycling. Lowering of MgATP reduced force and [V.sub.max]. The aorta was less sensitive to reduction in MgATP ([K.sub.m] for [V.sub.max]: 80 [micro]M) than the taenia coli ([K.sub.m] for [V.sub.max]: 350 [micro]M). Thus, velocity is controlled by steps preceding the ATP binding and cross-bridge dissociation, and a weaker binding of ATP is not responsible for the lower [V.sub.max] in the slow muscle. MgADP inhibited force and [V.sub.max]. Saturating concentrations of ADP did not completely inhibit maximal shortening velocity. The effect of ADP on [V.sub.max] was observed at lower concentrations in the aorta compared with the taenia coli, suggesting that the ADP binding to phosphorylated and cycling cross-bridges is stronger in slow compared with fast smooth muscle. KEY WORDS: myosin isoforms * phosphate * ATP * ADP * force-velocity relation

TNF-[Alpha] inhibits flow and insulin signaling leading to NO production in aortic endothelial cells. Am J Physiol Cell Physiol 280: C1057-C1065, 2001.--Endothelial cells release nitric oxide (NO) acutely in response to increased 'flow' or fluid shear stress (FSS), and the increase in NO production is correlated with enhanced phosphorylation and activation of endothelial nitric oxide synthase (eNOS). Both vascular endothelial growth factor and FSS activate endothelial protein kinase B (PKB) by way of incompletely understood pathway(s), and, in turn, PKB phosphorylates eNOS at Ser-1179, causing its activation. In this study, we found that either FSS or insulin stimulated insulin receptor substrate-1 (IRS-1) tyrosine and serine phosphorylation and increased IRS-1-associated phosphatidylinositol 3-kinase activity, phosphorylation of PKB Ser-473, phosphorylation of eNOS Ser-1179, and NO production. Brief pretreatment of bovine aortic endothelial cells with tumor necrosis factor-[Alpha] (TNF-[Alpha]) inhibited the above described FSS- or insulin-stimulated protein phosphorylation events and almost totally inhibited FSS- or insulin-stimulated NO production. These data indicate that FSS and insulin regulate eNOS phosphorylation and NO production by overlapping mechanisms. This study suggests one potential mechanism for the development of endothelial dysfunction in disease states with alterations in insulin regulation and increased TNF-[Alpha] levels. insulin receptor substrate-1; tyrosine phosphorylation; phosphatidylinositol 3-kinase; endothelial nitric oxide synthase phosphorylation; tumor necrosis factor-[Alpha]; nitric oxide

Rapacon-Baker, Michelle, Fan Zhang, Michael L. Pucci, Hui Guan, and Alberto Nasjletti. Expression of myogenic constrictor tone in the aorta of hypertensive rats. Am J Physiol Regulatory Integrative Comp Physiol 280: R968-R975, 2001.--We investigated the effect of intraluminal pressure or stretch on the development of tone in the descending thoracic aorta from rats with aortic coarctation-induced hypertension of 7-14 days duration. Increments of pressure [is greater than] 100 mmHg decreased the diameter of thoracic aortas from hypertensive but not from normotensive rats. The pressure-induced constriction was not demonstrable in vessels superfused with calcium-free buffer. Stretched rings of aorta from hypertensive rats exhibited a calcium-dependent constrictor tone accompanied by elevated calcium influx that varied in relation to the degree of stretch. Blockers of L-type calcium channels and inhibitors of protein kinase C reduced both basal tone and calcium influx in aortic rings of hypertensive rats. Hence, the thoracic aorta of hypertensive rats expresses a pressure- and stretch-activated constrictor mechanism that relies on increased calcium influx through L-type calcium channels via a protein kinase C-regulated pathway. The expression of such a constrictor mechanism is suggestive of acquired myogenic behavior. myogenic tone; protein kinase C; calcium influx; aortic smooth muscle; hypertension

Kleschyov, Andrei L., Bernard Muller, Therese Keravis, Marie-Elisabeth Stoeckel, and Jean-Claude Stoclet. Adventitia-derived nitric oxide in rat aortas exposed to endotoxin: cell origin and functional consequences. Am J Physiol Heart Circ Physiol 279: H2743-H2751, 2000.--The role of adventitial cells in bacterial lipopolysaccharide (LPS)-induced vascular nitric oxide (NO) overproduction has been largely ignored. In rat aortas exposed to LPS in vitro or in vivo, it was found that adventitia contained the major part of NO synthase (NOS)-2 protein (Western blot and immunohistochemistry) and generated the largest amount of NO (electron paramagnetic resonance spin trapping). NOS-2 immunoreactive cells were mainly resident macrophages at an early stage (5 h, in vitro or in vivo) and fibroblasts at a later stage (20 h, in vitro). Adventitial NOS-2 activity largely accounted for 1) the relaxing effect of L-arginine in rings exposed to LPS in vivo, 2) generation of an 'NO store' revealed by N-acetylcysteine-induced relaxation, and 3) formation of protein-bound dinitrosyl iron complexes in the medial layer of aortic rings exposed to LPS in vitro. In conclusion, the adventitia is a powerful source of NO triggered by LPS in the rat aorta. This novel source of NO has an important impact on smooth muscle function and might be implicated in various inflammatory diseases. adventitial fibroblasts; adventitial macrophages; dinitrosyl iron complexes; electron paramagnetic resonance spin trapping

Cifuentes, M. Eugenia, Federico E. Rey, Oscar A. Carretero, and Patrick J. Pagano. Upregulation of [p67.sup.phox] and [gp91.sup.phox] in aortas from angiotensin II-infused mice. Am J Physiol Heart Circ Physiol 279: H2234-H2240, 2000.--Although NAD(P)H oxidase-derived superoxide ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]) is increased during the development of angiotensin II (ANG II)-dependent hypertension, vascular regulation at the protein level has not been reported. We have shown that four major components of NAD(P)H oxidase are located primarily in the vascular adventitia as a primary source of vascular ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]). Here we compare vascular levels of ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]) and NAD(P)H oxidase in normotensive and ANG II-infused hypertensive mice and show that, after 7 days of ANG II infusion (7'50 [micro]g [multiplied by] [kg.sup.-1] [multiplied by] [day.sup.-1] ip) in C57B1/6 mice, systolic blood pressure was increased compared with that after sham infusion, concomitant with increased ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]) in the thoracic aorta as measured using lucigenin (25 [micro]M)-enhanced chemiluminescence. Both [p67.sup.phox] and [gp91.sup.phox] were detectable by Western blotting in aortic homogenates, and we observed increased protein levels of NAD(P)H oxidase subunits. These ANG II-induced increases were normalized by simultaneous treatment with the [AT.sub.1] receptor antagonist losartan. Moreover, the primary location of these subunits was the adventitia as detected immunohistochemically. Our results suggest that ANG II-induced increases in ([MATHEMATICAL EXPRSSION NOT REPRODUCIBLE IN ASCII]) are due to increased adventitial NAD(P)H oxidase activity, brought about by the heightened expression and interaction of its components. hypertension; superoxide anion; free radicals; reactive oxygen species; NAD(P)H oxidase; NAD(P)H oxidoreductase

Walters, F. S., M. Covarrubias, and J. S. Ellingson. Potent inhibition of the aortic smooth muscle maxi-K channel by clinical doses of ethanol. Am J Physiol Cell Physiol 279: C1107-C1115, 2000.--We investigated the effects of clinically relevant ethanol concentrations (5-20 mM) on the single-channel kinetics of bovine aortic smooth muscle maxi-K channels reconstituted in lipid bilayers (1:1 palmitoyl-oleoylphosphatidylethanolamine: palmitoyl-oleoyl-phosphatidylcholine). Ethanol at 10 and 20 mM decreased the channel open probability ([P.sub.o]) by 75 [+ or -] 20.3% mainly by increasing the mean closed time (+82 to +960%, n = 7). In some instances, ethanol also decreased the mean open time (-40.8 [+ or -] 22.5%). The [P.sub.o]-voltage relation in the presence of 20 mM ethanol exhibited a rightward shift in the midpoint of voltage activation ([Delta][V.sub.1/2] = 17 mV), a slightly steeper relationship (change in slope factor, [Delta]k, [congruent] -2.5 mV), and a decreased maximum [P.sub.o] (from ~0.82 to ~-0.47). Interestingly, channels inhibited by ethanol at low [Ca.sup.2+] concentrations (2.5 [micro]M) were very resistant to ethanol in the presence of increased [Ca.sup.2+] ([is greater than or equal to] 20 [micro]M). Alcohol consumption in clinically relevant amounts may alter the contribution of maxi-K channels to the regulation of arterial tone. calcium dependent; voltage-gated potassium channels; planar lipid bilayer; arterial tone; alcohol

Wronski, T., P. B. Persson, E. Seeliger, A. Harnath, and B. Flemming. Coupling of left ventricular and aortic volume elasticity in the rabbit. Am J Physiol Regulatory Integrative Comp Physiol 279: R539-R547, 2000.--Changes in volume elasticity (VE) of the left ventricle and aorta could be important for blood flow. A procedure is presented to rapidly assess VE of the left ventricle and aorta by analyzing changes in the eigenfrequency. Six control rabbits and 11 rabbits with atheromatosis (12 wk of high-cholesterol feeding) were studied. In control rabbits, during the first half of the systole, left ventricular VE continuously increased to +43% (P [is less than] 0.05). Then VE gradually declined to an end-diastolic minimum (20% of the average systolic levels, P [is less than] 0.05). Aortic VE changes were in the opposite direction to the ventricle. Aortic VE continuously decreased throughout the systole; the last value was 20% lower than at the beginning of the systole (P [is less than] 0.05). Conversely, diastolic VE of the aorta took on greater values. This inverse time course between ventricle and aorta may reduce energy requirements for conveying blood. High cholesterol-fed rabbits did not reveal the inverse behavior of ventricular and aortic VE, e.g., aortic VE increased during the systole (119%, P [is less than] 0.05). heart; aorta; compliance; left ventricular-arterial coupling; eigenfrequency; cholesterol; atherosclerosis

Atherosclerotic lesions form at distinct sites in the arterial tree, suggesting that hemodynamic forces influence the initiation of atherogenesis. If NF-[Kappa]B plays a role in atherogenesis, then the activation of this signal transduction pathway in arterial endothelium should show topographic variation. The expression of NF-[Kappa]B/I[Kappa]B components and NF-[Kappa]B activation was evaluated by specific antibody staining, en face confocal microscopy, and image analysis of endothelium in regions of mouse proximal aorta with high and low probability (HP and LP) for atherosclerotic lesion development. In control C57BL/6 mice, expression levels of p65, I[Kappa]B[Alpha], and I[Kappa]B[Beta] were 5- to 18-fold higher in the HP region, yet NF-[Kappa]B was activated in a minority of endothelial cells. This suggested that NF-[Kappa]B signal transduction was primed for activation in HP regions on encountering an activation stimulus. Lipopolysaccharide treatment or feeding low-density lipoprotein receptor knockout mice an atherogenic diet resulted in NF-[Kappa]B activation and up-regulated expression of NF-[Kappa]B-inducible genes predominantly in HP region endothelium. Preferential regional activation of endothelial NF-[Kappa]B by systemic stimuli, including hypercholesterolemia, may contribute to the localization of atherosclerotic lesions at sites with high steadystate expression levels of NF-[Kappa]B/I[Kappa]B components. atherosclerosis | p65 | I[Kappa]B[Alpha] | VCAM-1 | E-selectin

Neurotransmission of autonomic components of aortic baroreceptor afferents in the NTS of awake rats. Am J Physiol Heart Circ Physiol 279: H67-H75, 2000.--The effect of sequential blockade of N-methyl-D-aspartic acid (NMDA) receptors with DL-2-amino-5-phosphonopentanoic acid (AP-5) and non-NMDA receptors with 6,7-dinitroquinoxaline-2,3 dione (DNQX) in the nucleus tractus solitarii (NTS) on the cardiovascular responses to electrical stimulation (ES) of the aortic depressor nerve (ADN) was evaluated in awake rats. Two protocols were used. In protocol 1, bilateral microinjection of AP-5 into the NTS (n = 7) reduced the hypotensive response to ES of the ADN; subsequent microinjection of DNQX produced additional reduction in this response. AP-5 reduced the brady-cardic response, and DNQX almost abolished this response. In protocol 2, bilateral microinjection of DNQX into the NTS (n = 6) reduced the hypotensive response, and subsequent microinjection of AP-5 significantly reduced this response. DNQX produced a significant reduction in bradycardic response, and AP-5 abolished this response. The data indicate that processing of the parasympathetic component of the NTS aortic baroreceptor afferents is mediated by both NMDA and non-NMDA receptors, whereas processing of the sympathoinhibitory component seems to be only partially mediated by ionotropic receptors. baroreflex; excitatory amino acid receptors; N-methyl-o-aspartic acid receptors; non-N-methyl-o-aspartic acid receptors; bradycardia; hypotension; nucleus tractus solitarii

Aging is associated with adaptations in the hearts of mammals that diminish the reserve capacity to meet hemodynamic loading challenges. To evaluate potential mechanisms of this phenomenon, the following hypotheses were tested: compared with hearts of adult rats, hearts of aged rats undergoing aortic constriction will exhibit (a) a lower concentration of myofibrillar proteins, (b) a reduced sensitivity to extracellular calcium, and (c) a reduced coronary perfusion. Female Fischer 344 rats aged 9 months (adult) and 27 months (aged) were assigned to control (C) or aortic-constriction (AC) groups and studied at 7 and 28 days post-AC, yielding six groups of rats. Analysis of variance was used to examine the effects of age and AC. The left ventricular (LV) mass/body mass ratio expressed a percentage of age-matched control value averaged [AC-7.sub.adult], 111%; [AC-28.sub.adult], 120%; [AC-7.sub.aged], 106%; [AC-28.sub.aged], 123% (AC, p [is less than] .01). As a percentage of adult rats values, the pressure-generating capacity of the LV averaged [C.sub.aged], 99%; [AC-7.sub.aged], 92%; [AC-28.sub.aged], 92% (age, p [is less than] .05). There were no differences attributable to age or AC in either myofibrillar protein concentration or calcium sensitivity. There was, however, a significantly lower concentration of nonmyofibrillar protein (~10%) in the hearts of all three groups of aged rats compared with the adult rats that was unaltered by AC. The percentages of LV myosin heavy chain in the [Alpha]-isoform were [C.sub.adult], 77%; [AC-7.sub.adult], 66%; [AC-28.sub.adult], 66%; [C.sub.aged], 45%; [AC-7.sub.aged], 41%; [AC-28.sub.aged], 32% (age, p [is less than] .01; AC, p [is less than] .01). Coronary flow per gram of tissue averaged 9 % lower in all three of the aged groups compared with the adult rats and was not significantly affected by AC (age, p [is less than] .05). The data suggest that a reduction in nonmyofibrillar protein and a reduced coronary flow, rather than changes in calcium sensitivity or myofibrillar protein, are associated with an impairment in the adaptive response of the aged heart.

Endothelium modulates anion channel-dependent aortic contractions to iodide. Am J Physiol Heart Circ Physiol 278: H1527-H1536, 2000.--Anion currents contribute to vascular smooth muscle (VSM) membrane potential. The substitution of extracellular chloride (C1) with iodide (I) or bromide (Br) initially inhibited and then potentiated isometric contractile responses of rat aortic rings to norepinephrine. Anion substitution alone produced a small relaxation, which occurred despite a lack of active tone and minimal subsequent contraction of endothelium-intact rings (4.2 [+ or -] 1.2% of the response to 90 mM KCl). Endothelium-denuded rings underwent a similar initial relaxation but then contracted vigorously (I [is greater than] Br). Responses to 130 mM I (93.7 [+ or -] 1.9% of 90 mM KCl) were inhibited by nifedipine ([10.sup.-6] M), niflumic acid ([10.sup.-5] M), tamoxifen ([10.sup.-5] M), DIDS ([10.sup.-4] M), and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]-free buffer (HEPES 10 mM) but not by bumetanide ([10.sup.-5] M). Intact rings treated with N [Omega]-nitro-L-arginine ([10.sup.-4] M) responded weakly to I (15.5 [+ or -] 2.1% of 90 mM KCl), whereas hemoglobin ([10.sup.-5] M), indomethacin ([10.sup.-6] M), 17-octadecynoic acid ([10.sup.-5] M), and 1H[1,2,4] oxadiazole [4,3-a] quinoxalin-l-one ([10.sup.-6] M) all failed to augment the response of intact rings to I. We hypothesize that VSM takes up I primarily via an anion exchanger. Subsequent I efflux through anion channels having a selectivity of I [is greater than] Br [is greater than] Cl produces depolarization. In endothelium-denuded or agonist-stimulated vessels, this current is sufficient to activate voltage-dependent calcium channels and cause contraction. Neither nitric oxide nor prostaglandins are the primary endothelial modulator of these anion channels. If they are regulated by an endothelium-dependent hyperpolarizing factor it is not a cytochrome P-450 metabolite. nitric oxide; calcium channels; chloride channels; vascular smooth muscle; anion exchangers.

Yang, Zhi-Wei, Asefa Gebrewold, Maja Nowakowski, Bella T. Altura, and Burton M. Altura. [Mg.sup.2+]-induced endothelium-dependent relaxation of blood vessels and blood pressure lowering: role of NO. Am. J. Physiol. Regulatory Integrative Comp. Physiol. 278: R628-R639, 2000.--In vitro extracellular [Mg.sup.2+] concentration ([[[Mg.sup.2+]].sub.0]) produces endothelium-dependent and endothelium-independent relaxations in rat aorta in a concentration-dependent manner. These relaxant effects of [Mg.sup.2+] on intact rat aortic rings, but not denuded rat aortic rings, were suppressed by either [N.sup.G]-monomethyl-L-arginine (L-NMMA), [N.sup.[Omega]]-nitro-L-arginine methyl ester (L-NAME), or methylene blue. The inhibitory effects of L-NMMA and L-NAME could be reversed partly by L-arginine. [[[Mg.sup.2+]].sub.0]- induced dilatation in vivo in rat mesenteric arterioles and venules was almost completely inhibited by [N.sup.G]-nitro-L-arginine and L-NMMA. Removal of extracellular [Ca.sup.2+] concentration ([[[Ca.sup.2+]].sub.0]) or buffering intracellular [Ca.sup.2+] concentration in endothelial cells, with 10 [micro]M 1,2-bis(2-aminophenoxy)-ethane-N,N,N', N'-tetraacetic acid-AM, markedly attenuated the relaxant effects of [Mg.sup.2+]. [Mg.sup.2+] produced nitric oxide (NO) release from the intact aortic rings in a concentration-dependent manner. Removal of [[[Ca.sup.2+]].sub.0] diminished the increased NO release induced by elevated levels of [[[Mg.sup.2+]].sub.0]. In vivo infusion of increasing doses (1-30 [micro]M/min) of Mg[SO.sub.4], directly into the femoral veins of anesthetized rats, elicited significant concentration-dependent sustained increases in serum total Mg and concomitant decreases in arterial blood pressure. Before and after employment of various doses of Mg[SO.sub.4], intravenous administration of either L-NMMA (10 mg/kg) or L-NAME (10 mg/kg) increased (i.e., reversed) the [MgSO.sub.4]-lowered blood pressure markedly, and intravenous injection of L-arginine restored partially the increased blood pressure effects of both L-NMMA and L-NAME. Our results suggest that 1) small blood vessels are very dependent on NO release for [Mg.sup.2+] dilatations and 2) the endothelium-dependent relaxation induced by extracellular [Mg.sup.2+] is mediated by release of endothelium-derived relaxing factor-NO from the endothelium, and requires [Ca.sup.2+] and formation of guanosine 3',5'-cyclic monophosphate. rat aorta; microvessels; calcium; endothelium-derived relaxing factor; vasodilatation; guanosine 3',5'-cyclic monophosphate

Kissling, G., B. Blickle, and U. Pascht. Modified heart-lung preparation for the evaluation of systolic and diastolic coronary flow in rats. Am. J. Physiol. Heart Circ. Physiol. 278: H277-H284, 2000.--A modified heart-lung preparation of the rat, which permits measuring systolic and diastolic coronary flow separately and enables coronary compliance to be evaluated, is described. The systemic circulation was substituted by a shunt circuit, and the elastic properties of the arterial tree were mimicked by a rubber balloon. Systolic and diastolic coronary flow was evaluated from the pulmonary and aortic flow signal. Integrated phasic pulmonary flow represented right ventricular stroke volume. Integrated phasic systolic aortic flow represented left ventricular stroke volume minus that volume flowing into the coronary arteries during systole, because the aortic flow probe had to be inserted distal to the origin of the coronary vessels. Because right and left ventricular stroke volume was identical under steady-state conditions, the difference between systolic pulmonary and systolic aortic flow resulted in systolic coronary flow. Diastolic coronary flow was measured by means of the retrograde flow through the aortic flow probe. Coronary compliance was calculated according to Frank's windkessel model from coronary resistance and from central diastolic aortic pressure, which decayed exponentially after switching out the rubber balloon and the shunt circuit. It could be shown that the proportion of systolic to diastolic coronary flow depends on coronary compliance. coronary compliance; coronary capacitance flow

Ying, Wei-Zhong, and Paul W. Sanders. Dietary salt increases endothelial nitric oxide synthase and TGF-[Beta] 1 in rat aortic endothelium. Am. J. Physiol. 277 (Heart Circ. Physiol. 46): H1293-H1298, 1999.--The amount of NaCl in the diet plays an important role in modulating nitric oxide (NO) synthesis in vivo. In the glomerulus, dietary NaCl also regulates transforming growth factor-[Beta] 1 (TGF-[Beta] 1) production. We hypothesized that dietary NaCl intake regulated expression of the endothelial isoform of nitric oxide synthase (NOS3) and TGF-[Beta] 1 in the aorta. Administration of 8.0% NaCl diet to rats for 7 days did not affect blood pressure but increased steady-state mRNA and protein levels of NOS3 in the arterial wall compared with animals on 0.3% NaCl diet. Northern analysis demonstrated increased steady-state amounts of mRNA of TGF-[Beta] 1 in aortas of rats on 8.0% NaCl diet. By ELISA, both total and active TGF-[Beta] 1 were increased in these vessel segments. Endothelial denudation of aortic rings reduced active TGF-[Beta] 1 secretion to undetectable levels. Addition of a neutralizing antibody to TGF-[Beta] to aortic ring segments attenuated NO production but not to that observed in animals on the 0.3% NaCl diet. The data showed that dietary NaCl intake modulated NOS3 and TGF-[Beta] 1 expression in the arterial wall; NOS3 expression was at least partially regulated by endothelial cell production of TGF-[Beta] 1. transforming growth factor-[Beta] 1; nitric oxide; sodium chloride; Sprague-Dawley rat

Aortic compliance is the ability of the aorta, the major blood vessel supplying the body, to distend in response to changes in blood pressure. It is the major factor determining blood pressure and the force against which the heart must pump blood. Factors that may control aortic compliance include preload, the pressure of the ventricle at the end of the relaxation phase of the heart cycle, and adrenergic activity, the activity of the sympathetic nervous system which functions in response to stress. The relation of preload and adrenergic activity to aortic compliance were examined in ten normal subjects and nine patients with hypertension, or high blood pressure, during rest and under conditions of low blood pressure. At rest, aortic compliance was lower in hypertensive patients than in normal subjects, and correlated inversely with blood pressure in both groups. Preload, measured by pulmonary wedge pressure, was greater in hypertensive patients than normal subjects, and adrenergic activity was similar in both groups; neither preload nor adrenergic activity were correlated with aortic compliance at rest. Under conditions of lowered blood pressure, preload and adrenergic activity were similar in both normal subjects and hypertensive patients, although normal subjects had significant increases in heart rates and decreases in compliance than hypertensive patients. Aortic compliance appears to be more regulated in normal patients than hypertensive patients, which may have important implications for the treatment of high blood pressure. (Consumer Summary produced by Reliance Medical Information, Inc.)

[Ca.sup.2+] influx mediates enhanced [[alpha].sub.2]-adrenergic contraction in aortas from rats treated with NOS inhibitor. Am J Physiol Heart Circ Physiol 281: H2233-H2240, 2001.--Previously, we reported that aortic segments from rats made hypertensive with the nitric oxide synthase inhibitor [N.sup.[omega]]-nitro-L-arginine (L-NNA) exhibit enhanced contractile sensitivity to both [[alpha].sub.2]-adrenergic receptor ([[alpha].sub.2]-AR) stimulation and to KCl-induced depolarization. We hypothesized that increased contractile responses to these agents was due to a change in the common effector L-type voltage-dependent calcium channel (VDCC). In aortic segments from control and L-NNA-treated rats, contraction to the [[alpha].sub.2]-AR agonist UK-14304 stimulated [Ca.sup.2+] influx but released intracellular [Ca.sup.2+] only in control arteries. UK-14304-induced contraction was blocked by the VDCC antagonist nifedipine in both control and L-NNA aortas but contraction of aortas from L-NNA-treated rats was blocked by lower concentrations. Calcium imaging studies in fura 2-loaded freshly isolated aortic vascular smooth muscle cells also demonstrated UK-14304-stimulated [Ca.sup.2+] influx sensitive to nifedipine only in cells from L-NNA-treated rats. We conclude that [[alpha].sub.2]-AR contraction in the rat aorta is mediated primarily by [Ca.sup.2+] influx and that L-NNA-induced hypertension increases the dependence of this contraction on VDCCs. [N.sup.[omega]]-nitro-L-arginine; [[alpha].sub.2]-adrenergic receptor; UK-14304; vascular smooth muscle cells; L-type voltage-dependent calcium channels; nifedipine; hypertension

A culture system of swine coronary microvascular endothelial cells (MVEC) with high cellular yield and purity was established. In aortic endothelial cells (AEC), nitric oxide synthase activity (NOS) was 80 +/- 10 and was almost abolished in the absence of calcium. In primary MVEC, however, NOS III activity in the presence and absence of calcium was 20 +/- 4 and 25 +/- 5, respectively. Thus, cardiac MVEC, in contrast to AEC, contain alpha-smooth muscle actin, exhibit low-grade NOS III activity, and provide an appropriate in vitro system for investigating endothelial pathophysiology.