bluuebunny/crossref_metadata_2025 huggingface dataset:
Reversal of hypertension and endothelial dysfunction in deoxycorticosterone-NaCl-treated rats by high-Ca2+ diet
Authors: Makynen H. , Kahonen M. , Wu X. , Wuorela H. , Porsti I.
Published: December 2017

We tested the effect of high-Ca2+ diet on blood pressure and responses of mesenteric arterial rings in vitro in established deoxycorticosterone (DOC)-NaCl hypertension. Ca2+ supplementation (2.5%) of Wistar rats, which was commenced 8 wk after initiation of DOC-NaCl treatment (Ca(2+)-DOC group), reversed the development of hypertension, whereas in animals ingesting a normal diet (1.1% Ca2+; DOC group) blood pressure continued to rise until the end of the 12-wk study. In norepinephrine-precontracted arterial rings, relaxations to acetylcholine (ACh) and sodium nitroprusside were attenuated in the DOC group, but these responses were significantly improved by Ca2+ supplementation. The nitric oxide (NO) synthesis inhibitor NG-nitro-L-arginine methyl ester, in the presence of diclofenac, totally abolished ACh-induced relaxations in the DOC group but only attenuated them in the Ca(2+)-DOC group. The remaining relaxation was further inhibited by apamin, an inhibitor of Ca(2+)-activated K+ channels, and practically abolished after blockade of ATP-dependent K+ channels by glyburide. Interestingly, when endothelium-dependent hyperpolarization was prevented using precontractions induced by KCl, no differences were found in relaxations to ACh between the groups. In conclusion, high-Ca(2+) diet effectively reduced blood pressure in DOC-NaCl hypertension and concomitantly enhanced arterial relaxation. Because the relaxations to ACh in the Ca(2+)-DOC group were augmented in the absence and presence of NO synthesis inhibition but not under conditions of prevented hyperpolarization, these enhanced relaxations could be attributed to promoted endothelium-dependent hyperpolarization in the Ca(2+)-supplemented animals.
Effects of nonanticoagulant heparin on cardiovascular and hepatocellular function after hemorrhagic shock
Authors: Wang P. , Ba Z. F. , Reich S. S. , Zhou M. , Holme K. R. , Chaudry I. H.
Published: December 2017

Although heparinization of animals before hemorrhage improves cell and organ function, the potent anticoagulant activity of conventional heparin sodium precludes its potential clinical use. To determine whether a novel nonanticoagulant heparin, GM1892, would have any beneficial effects on cardiovascular and hapatocellular functions and would decrease susceptibility to sepsis after hemorrhage, laparotomy was performed on rats (i.e., trauma induced), after which they were bled to and maintained at a mean arterial pressure of 40 mmHg until 40% of maximal bleedout volume was returned in the form of Ringer lactate solution (RL). The rats were then resuscitated with three times the volume of shed blood with RL over 45 min, followed by infusion of two times RL plus GM1892 (7 mg/kg body wt; approximately 2% the anticoagulant activity of regular heparin) of saline over 60 min. At 2 and 4 h after the completion of resuscitation, cardiac output, hepatocellular function, and microvascular blood flow were determined. The results indicated that cardiac output, hepatocellular function, and microvascular blood flow in the liver, spleen, and small intestine decreased significantly after hemorrhage and resuscitation. Administration of GM1892, however, restored these parameters. The morphological abnormality observed after hemorrhage in the liver, kidney, and small gut was also attenuated with GM1892 treatment. Moreover, GM1892 normalized the elevated plasma prostaglandin E2 levels. Sepsis was induced in additional rats by cecal ligation and puncture (CLP) 20 h after hemorrhage, and the necrotic cecum was excised 10 h thereafter. GM1892 treatment significantly decreased mortality after CLP and cecal excision. Thus GM1892 appears to be a useful adjunct to fluid resuscitation, since it restores the depressed cardiovascular responses and decreases susceptibility to sepsis after trauma and hemorrhage.
PGE2 and PGI2 inhibit ET-1 secretion from endothelial cells by stimulating particulate guanylate cyclase
Authors: Razandi M. , Pedram A. , Rubin T. , Levin E. R.
Published: December 2017

Prostaglandins (PG)E2 and prostacyclin (PGI2) can cause vasodilation in selective vascular beds and could act in part by inhibiting the production of the vasoconstrictor endothelin-1 (ET-1). We recently reported that these prostanoids inhibit ET-1 production/secretion from cultured endothelial cells via the generation of guanosine 3'-5'-cyclic monophosphate (cGMP). It is unclear whether this results from the stimulation of the particulate (membrane) of soluble (cytosolic) form of guanylate cyclase, and whether these effects are through an intermediate, such as nitric oxide. PGE2 and PGI2 each caused a three- to fourfold increase in both membrane and whole bovine aortic endothelial cell guanylate cyclase activity. The stimulations were significantly reversed (80-90%) by the compound LY-83583, an antagonist to cGMP generation, but were unaffected by methylene blue (MB), an inhibitor of nitric oxide-induced soluble guanylate cyclase. In contrast, the prostaglandins did not generate cGMP in cytosolic fractions. The prostaglandins inhibited ET-1 secretion from the intact cells, which was significantly prevented by LY-83583, but not by MB. Neither prostaglandin stimulated NO synthase activity, an indicator of nitric oxide generation. We conclude that PGE2 and PGI2 are likely to inhibit ET-1 secretion through the activation of the particulate guanylate cyclase, identifying a novel mechanism by which the prostanoids signal in the endothelial cell.
Identification and characteristics of delayed rectifier K+ current in fetal mouse ventricular myocytes
Authors: Wang L. , Duff H. J.
Published: December 2017

Although the genetics of mammalian cardiac K+ channels have been most intensively investigated in mice, there are limited data available from the electrophysiological studies of the K+ currents in native mouse cardiac myocytes, especially in fetal mouse heart. The present study utilized whole cell patch-clamp techniques to assess the delayed rectifier K+ current (IK) in fetal (18th day of gestation) mouse ventricular myocytes. IK in fetal mouse ventricular myocytes activated rapidly, displayed a negative slope conductance of the current-voltage relationships at test potentials > 0 mV, satisfied the envelope of IK-tail test for a single component, and was very sensitive to dofetilide. These characteristics confirm that this current is the rapidly activating component of IK known as IK,r. In addition, dofetilide dramatically prolonged action potential duration in single ventricular myocytes as well as in ventricular myocardium, suggesting that IK,r plays a dominant role in action potential repolarization in fetal mouse heart. From these data we can conclude that fetal mouse cardiac myocytes express IK,r, which functions as a dominant repolarizing K+ current.
Quantitative beat-to-beat analysis of heart rate dynamics during exercise
Authors: Tulppo M. P. , Makikallio T. H. , Takala T. E. , Seppanen T. , Huikuri H. V.
Published: December 2017

Beat-to-beat heart rate (HR) dynamics were studied by plotting each R-R interval as a function of the previous R-R interval (Poincare plot) during incremental doses of atropine followed by exercise for 10 subjects and during exercise without autonomic blockade for 31 subjects. A quantitative two-dimensional vector analysis of a Poincare plot was used by measuring separately the standard deviation of instantaneous beat-to-beat R-R interval variability (SD1) and the standard deviation of continuous long-term R-R interval variability (SD2) as well as the SD1/SD2 ratio. Quantitative Poincare measures were compared with linear measures of HR variability (HRV) and with approximate entropy (ApEn) at rest and during exercise. A linear progressive reduction was observed in SD1 during atropine administration, and it remained almost at the zero level during exercise after a parasympathetic blockade. Atropine resulted in more variable changes in SD2 and the SD1/SD2 ratio, but during exercise after parasympathetic blockade, a progressive increase was observed in the SD1/SD2 ratio until the end of exercise. The SD1/SD2 ratio had no significant correlations with the frequency domain measures of HRV. However, the SD1/SD2 ratio had a modest correlation with ApEn at rest (r = -0.69, P < 0.001), but not during exercise (r = 0.27, P = NS). All measures of vagal modulation of HR decreased progressively until the ventilatory threshold level was reached, when sympathetic activation was reflected as changes in the SD1/SD2 ratio. These results show that quantitative two-dimensional vector analysis of a Poincare plot can provide useful information on vagal modulation of R-R interval dynamics during exercise that are not easily detected by linear summary measures of HRV or by ApEn.
Decreased sensitivity to vasoconstrictors in aortic rings after acute exposure to nitric oxide
Authors: Kanagy N. L. , Charpie J. R. , Dananberg J. , Webb R. C.
Published: December 2017

Nitric oxide (NO) has been postulated as a regulator of vascular reactivity, and the current study tested the hypothesis that NO-induced decreased sensitivity to vasoconstrictors persists following removal of NO. Endothelium-denuded segments of rat aorta were incubated 2-4 h at 37 degrees C with the NO donor S-nitroso-N-acetylpenicillamine (SNAP). Incubation produced rightward shifts in concentration response curves for phenylephrine [i.e., half-maximum effective concentration (EC50; in microM): control = 0.016, NO = 0.14], aluminum fluoride (i.e., EC50 in mM: control = 1.66, NO = 2.29), and KCl (i.e., EC50 in mM: control = 5.9, NO = 23.9). Similar shifts were seen for two other NO donors. The SNAP-induced shift was not attenuated by a guanylyl cyclase inhibitor, LY-83583 (10 microM) and was not mimicked by 8-bromoguanosine 3',5'-cyclic monophosphate (100 microM). It was attenuated by 1,4-naphthoquinone (50 microM), an inhibitor of endogenous mono-ADP ribosyltransferases. NO incubation increased cGMP content (4.6 +/- 0.8 vs. 1.5 +/- 0.15 pmol/mg protein), an increase unaffected by 1,4-naphthoquinone (3.3 +/- 1.0 pmol/mg protein) but prevented by LY-83583 (1.6 +/- 0.36 pmol/mg protein). ADP ribosylation of three proteins was observed in membranes from HEK 293 cells: 88,66, and 38 kDa. ADP ribosylation of the 38-kDa protein was stimulated in a concentration-dependent manner by NO but was not decreased by 1,4-naphthoquinone. In conclusion, NO produces a long-lasting inhibition of vascular contractility by both a cGMP-dependent and -independent mechanism. Based on the observations of 1,4-naphthoquinone, we conclude that the cGMP-independent mechanism is not stimulation of endogenous ADP ribosylation but some other covalent modification in the pathway that mediates contraction.
Effect of endothelin antagonism on blood pressure and vascular structure in renovascular hypertensive rats
Authors: Li J. S. , Knafo L. , Turgeon A. , Garcia R. , Schiffrin E. L.
Published: December 2017

To investigate the potential pathogenic role of endothelin in blood pressure elevation and vascular hypertrophy in renovascular hypertensive rats, which present twofold elevations in endothelin-1 mRNA abundance in blood vessels, the response of blood pressure and vascular structure to chronic treatment with the endothelin receptor antagonist bosentan was evaluated. One-kidney, one clip (1K,1C) and two kidney, one clip (2K,1C) Goldblatt hypertensive rats were treated for 2 wk with bosentan (100 mg.kg-1.day-1) in their chow, and systolic blood pressure was measured by the tail-cuff method. Vascular structure was studied in small arteries mounted on a wire myograph. Treatment with bosentan did not result in a significant change in systolic blood pressure or in the structure of small coronary, renal cortical, mesenteric, or femoral arteries in 1K, 1C or in 2K, 1C hypertensive rats. In conclusion, modest (twofold) elevations of endothelin-1 gene expression in blood vessels in renovascular hypertension are not associated with hypotensive responses or regression of vascular hypertrophy during treatment with endothelin antagonists in contrast to what is found in deoxycorticosterone acetate salt hypertensive rats, which exhibit very dramatic increases in endothelin-1 expression (five-to eightfold) and do respond to endothelin antagonism with blood pressure lowering and regression of vascular hypertrophy. These small elevations of vascular endothelin-1 gene expression thus do not appear to indicate the presence of an endothelin component in blood pressure elevation in renovascular hypertension in rats.
Nonlinear analysis of BP signal. Can it detect malfunctions in BP control?
Authors: Almog Y. , Eliash S. , Oz O. , Akselrod S.
Published: December 2017

In the present study, our aim was to evaluate the applicability of the nonlinear technique to the investigation of cardiovascular control. We applied an approach known as the “surrogate data method” to test for nonlinear components in the blood pressure (BP) signal. Our results strongly indicate that there are nonlinear components in the BP time series taken from a Wistar-Kyoto rat (WKY), suggesting that the use of nonlinear methods may provide new information about the BP control system. We developed a procedure appropriate for the stable and reliable calculation of the Grassberger-Procaccia correlation dimension (D) of the arterial BP signal. The saturation value D was 5.48 +/- 0.30 for the WKY group and 5.92 +/- 0.26 for the spontaneously hypertensive rat (SHR) group, with P < 0.001. We also found that in the WKY group D displays a significant response to complete alpha 1 blockade and bleeding, whereas no response is observed in the SHR group. These results imply that differences in the control mechanisms may be detected by the nonlinear dynamics approach both under baseline conditions and when interfering with cardiovascular control.
Protection of reoxygenated cardiomyocytes against osmotic fragility by nitric oxide donors
Authors: Schluter K. D. , Jakob G. , Ruiz-Meana M. , Garcia-Dorado D. , Piper H. M.
Published: December 2017

In ischemic-reperfused myocardium, myocardial cells are jeopardized not only by reoxygenation-induced hypercontracture but also by the development of a transsarcolemmal osmotic gradient. Here the question of whether osmotic fragility of cardiomyocytes can be reduced by interventions during reoxygenation was addressed. Isolated ventricular cardiomyocytes (from adult rats), exposed to 120 min of hypoxia and subsequent reoxygenation, were used as model. With reoxygenation, medium osmolarity was reduced from 270 to 80 mosM. Loss of sarcolemmal integrity was characterized by enzyme loss from cells (creatine kinase and lactate dehydrogenase). Cardiomyocytes reoxygenated after 120 min of hypoxia hypercontracted, but enhanced enzyme loss was observed only at 80 mosM. The nitric oxide (NO) donors 3-morpholinosydnonimine (10 mM), sodium nitroprusside (10 mM), S-nitroso-N-acetyl-DL-penicillamine (100 microM), and the antilipid peroxidant diphenylphenylenediamine (DPPD, 2.5 microM) reduced enzyme loss with hyposmolar reoxygenation. Agents activating guanosine 3',5'-cyclic monophosphate (cGMP)-dependent pathways [atrial natriuretic peptide (1 microM), urodilatin (1 microM), and 8-bromo-cGMP (10 mM)], the contractile inhibitor 2,3-butanedione monoxime (10 mM), and the SIN-1 metabolite SIN-1C (10 mM) did not protect cardiomyocytes against osmotic fragility. The results show that increased osmotic fragility of isolated adult rat cardiomyocytes can be prevented at the time of reoxygenation by NO donors and DPPD in a cGMP-independent way.
Parasympathetic denervation supersensitivity of the transplanted human ventricle in vivo
Authors: Koglin J. , Uberfuhr P. , von Scheidt W.
Published: December 2017

Sympathetic inotropic supersensitivity after transplantation-associated denervation of the cardiac autonomic nervous system has been described in humans previously. Potential changes of the parasympathetic regulation of the human ventricular contractility have not been investigated yet. We studied the antiadrenergic, negative inotropic effect of carbachol (3.6 micrograms/kg) during continuous beta-adrenergic stimulation (with isoproterenol, 20 ng.kg-1.min-1) in seven heart transplant recipients and seven healthy controls. Changes in ventricular contractility were calculated as increase of the systolic pressure-to-dimension ratio (delta P/D) and the rate-corrected velocity of circumferential fiber shortening (delta Vcfc), using M-mode echocardiography. In the control group, the isoproterenol-induced increase in contractility was attenuated only insignificantly by carbachol [delta P/D from 1.53 +/- 0.53 to 0.81 +/- 0.55 mmHg/mm, delta Vcfc from 0.77 +/- 0.20 to 0.63 +/- 0.22% x square root of beats/min (bpm)/ms]. In contrast, the transplant group exhibited a significant reduction of the isoproterenol-induced increase in contractility [delta P/D from 1.27 +/- 0.71 to -0.81 +/- 0.51 mmHg/mm (P < 0.01), delta Vcfc from 1.04 +/- 0.84 to 0.04 +/- 0.43% x square root of bpm/ms (P < 0.01)]. These data are consistent with parasympathetic indirect negative inotropic supersensitivity of the transplanted human heart in vivo.
Effect of heparin on fibrinolytic activity and platelet function in vivo
Authors: Upchurch G. R. , Valeri C. R. , Khuri S. F. , Rohrer M. J. , Welch G. N. , MacGregor H. , Ragno G. , Francis S. , Rodino L. J. , Michelson A. D. , Loscalzo J.
Published: December 2017

Heparin, a polyanionic glycosaminoglycan, is used routinely before the induction of cardiopulmonary bypass. Earlier observations in our laboratory suggested that the postoperative bleeding that occurs, despite neutralization of heparin with protamine, is secondary to hypothermia and dilutional anemia during bypass. An additional, potential mechanism for excessive bleeding following cardiopulmonary bypass is that heparin activates the fibrinolytic system, which may, in turn, adversely affect hemostasis. To understand better the effects of heparin administration on the fibrinolytic system in vivo, we simulated the anticoagulant regimen of cardiopulmonary bypass by administering increasing doses of intravenous heparin to five adult baboons over 60 min. We measured fibrinolytic parameters serially following heparinization and demonstrated that heparin induces activation of the fibrinolytic system. We showed that the fibrinolytic system was activated in vivo as evidenced by an increase in plasmin activity and immunoreactive plasmin light chain, as well as an increase in immunoreactive fibrinogen fragment E in vitro. These results demonstrate that the fibrinolytic system is activated in vivo by the administration of heparin during cardiopulmonary bypass. These data suggest that, despite administration of a neutralizing agent such as protamine, heparin may contribute to postoperative bleeding complications following cardiopulmonary bypass surgery owing principally to its longer lived effects on the fibrinolytic system.
Calcium-and phorbol ester-dependent calponin phosphorylation in homogenates of swine carotid artery
Authors: Rokolya A. , Walsh M. P. , Moreland R. S.
Published: December 2017

Calponin inhibits actin-activated myosin adenosinetriphosphatase (ATPase) activity, and phosphorylation reverses this inhibition. Calponin phosphorylation has been demonstrated in reconstituted contractile protein systems, but studies using intact smooth muscle have produced mixed results. The goal of this study was to determine if vascular smooth muscle contains the necessary biochemical machinery to catalyze calponin phosphorylation. We used swine carotid homogenate, which allows access to the intracellular components and contains all endogenous proteins and enzymes in physiologically relevant concentrations. We demonstrated that calponin is phosphorylated in response to Ca2+ (0.27 +/- 0.04 mol P(i)/mol calponin) and in response to phorbol 12,13-dibutyrate in the presence or absence of Ca2+ (0.48 +/- 0.09 mol P(i)/mol calponin). Calponin phosphorylation was inhibited by the protein kinase C inhibitor staurosporine but not by the Ca(2+)- and calmodulin-dependent protein kinase II inhibitor KN-62. We conclude that Ca(2+)-dependent and -independent isoforms of protein kinase C but not the Ca(2+) -and calmodulin-dependent protein kinase II catalyze calponin phosphorylation in the swine carotid artery.
Role of ANG II in hypertension produced by chronic inhibition of nitric oxide synthase in conscious rats
Authors: Melaragno M. G. , Fink G. D.
Published: December 2017

These experiments tested the hypothesis that hypertension caused by chronic inhibition of nitiric oxide synthase (NOS) is associated with augmented pressor responsiveness to angiotensin II (ANG II). Antagonism of ANG II AT1 receptors with losartan caused a greater fall in blood pressure (BP) in rats treated for 2 wk with the NOS inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) than in normotensive rats. The delayed time course of the decline in BP implicated the slow pressor effect (SPE) of ANG II in L-NAME hypertension. Further experiments showed that direct elicitation of the SPE by continuous low-dose (4 ng/min) intravenous infusion of ANG II in enalapril-treated rats resulted in a larger chronic increase in BP if NOS was inhibited. However, L-NAME alone also caused a significant increase in BP in enalapril-treated rats. The combined effect on BP of ANG II and L-NAME was merely additive. These results confirm that ANG II is involved in L-NAME hypertension. However, chronic pressor responsiveness to the peptide is not augmented by L-NAME.
Role of parabrachial nucleus in baroreflex-mediated coronary vasoconstriction
Authors: Gutterman D. D. , Goodson A.
Published: December 2017

Coronary vasoconstriction is a component of the baroreflex response to bilateral carotid occlusion. The central pathways responsible for this reflex constriction are incompletely understood, but previous studies show that activation of parabrachial nucleus (PBN) elicits coronary vasoconstriction and that PBN shares prominent anatomic connections with other central baroreflex centers, including the nucleus of the tractus solitarius. Therefore, we examined whether PBN plays a role in baroreflex mediated coronary constriction and whether cell bodies rather than fibers passing through this region are involved. Anesthetized cats were instrumented for continuous measurements of heart rate, arterial pressure, and coronary flow velocity. Bilateral carotid occlusion following propranolol and vagotomy increased arterial pressure (63 +/- 10%) and an index of coronary vascular resistance (34 +/- 6%). Bilateral microinjections of lidocaine (1%, 400 nl) into PBN reversibly attenuated the coronary constriction (19 +/- 5%) with little effect on the change in arterial pressure. It was further demonstrated that autoregulatory responses to the increase in pressure could not fully account for the observed changes in coronary constriction. In a separate group of animals, kainic acid (50 mM, 300 nl) abolished the baroreflex increase in coronary resistance (43 +/- 1 vs. -9 +/- 9% after) without affecting the increase in arterial pressure (54 +/- 12% increase before vs. 55 +/- 20% increase after kainic acid). We conclude that PBN is a necessary component of the baroreflex pathway mediating coronary vasoconstriction. Furthermore, cell bodies in PBN, rather than simply fibers passing through that region, participate in the reflex coronary vasoconstriction.
Comparison of two techniques for measuring two-dimensional strain in rat left ventricles
Authors: Omens J. H. , Farr D. D. , McCulloch A. D. , Waldman L. K.
Published: December 2017

Measurements of regional deformation in the left ventricle are needed to understand the structural basis of ventricular function. Two techniques were employed to measure two-dimensional strain in the intact, beating rat heart. Rats were anesthetized and ventilated, and the chest of each rat was opened. Homogeneous two-dimensional strains were measured during the cardiac cycle relative to end diastole with either a triangle of miniature (0.3-0.5 mm) piezoelectric crystals implanted at midwall or with three epicardial surface markers imaged with a 60-Hz video system. Average heart rate was 303 +/- 37 beats/min, end-diastolic pressure was 2 +/- 2 mmHg, and peak-systolic pressure was 106 +/- 31 mmHg in all of the hearts. In general, strains during the cardiac cycle showed similar trends to those previously reported in the dog. The magnitudes of peak systolic cardiac strains on the epicardium and at midwall were -0.076 +/- 0.055, -0.068 +/- 0.014 (circumferential), -0.102 +/- 0.040, -0.082 +/- 0.039 (longitudinal), and 0.065 +/- 0.016, 0.064 +/- 0.043 (in-plane shear). There were mechanical side effects due to the crystal implantation that may limit the usefulness of this technique in its present form in the contracting rat heart. The epicardial surface technique does not have these side effects and will allow measurements of regional systolic cardiac function in rats with pathological interventions or genetic modifications that may alter regional ventricular function.
Elevated pressure stimulates protooncogene expression in isolated mesenteric arteries
Authors: Allen S. P. , Liang H. M. , Hill M. A. , Prewitt R. L.
Published: December 2017

The aim of this study was to determine whether an increase in pressure alone is a sufficient stimulus in isolated small arteries to induce the immediate early genes that are associated with vascular wall growth. Mesenteric arteries (303-506 microm diam) were isolated from Wistar rats and subjected to static pressure of 90 mmHg (control) or 140 mmHg (hypertensive). The arteries possessed little active tone or myogenic response to pressure elevation; therefore, both sets of vessels were stretched by similar amounts, but wall stress in the hypertensive vessels was 60-80% above that of controls. After 30, 60, 180, and 360 min, the arteries were fixed in Formalin, embedded in paraffin, and sectioned for in situ hybridization. The levels of mRNA for c-fos increased in the hypertensive arteries 2.33-fold at 30 min and 6.64-fold at 60 min. mRNA for c-myc increased 5.13-fold at 60 min and 5.25-fold at 180 min. After this early response gene induction, 18S rRNA increased in hypertensive vessels: 3.35-fold at 180 min and 4.2-fold at 360 min. These changes were not the result of a nonspecific activation of total gene expression in hypertensive vessels, inasmuch as levels of mRNA for beta-actin did not differ from controls; however, hypertensive and control vessels showed increases at 60 min. These results indicate that increased pressure is a sufficient stimulus for protooncogene induction and rRNA production in vascular smooth muscle cells in the arterial wall and suggest that the mechanical signal is wall stress. Therefore, this model represents a unique tool to complement cultured cells for the study of the signaling pathways in the mechanotransduction of a pressure stimulus.
Impairment of cGMP- and cAMP-mediated vasorelaxations in rats with chronic heart failure
Authors: Nasa Y. , Toyoshima H. , Ohaku H. , Hashizume Y. , Sanbe A. , Takeo S.
Published: December 2017

To elucidate pathophysiological alterations in vascular relaxation in rats with chronic heart failure (CHF), guanosine 3',5'-cyclic monophosphate (cGMP)- and adenosine 3',5'-cyclic monophosphate (cAMP)-mediated vasorelaxations in pulmonary artery (PA) and thoracic aorta (TA) of rats were examined 12 wk after coronary artery ligation. Acetylcholine (ACh)-induced relaxation was attenuated in endothelium-intact segments of both arteries, whereas sodium nitroprusside-induced relaxation was attenuated only in endothelium-intact TA segments of rats with CHF. Vasorelaxations elicited by isoproterenol and NKH-477, a water-soluble forskolin analogue, were diminished mainly in PA segments of the CHF rat. NG-nitro-L-arginine methyl ester (L-NAME)-induced decrease in cGMP level was less in endothelium-intact TA segments of the rat with CHF (0.20 +/- 0.06 vs. 0.99 +/- 0.26 pmol/mg protein in control), suggesting that basal nitric oxide (NO) production is reduced in CHF. Treatment with L-NAME attenuated the isoproterenol-induced relaxation only in endothelium-intact TA segments in control rats but not in CHF rats. The results suggest that both cGMP- and cAMP-mediated relaxations are impaired in CHF, and a reduction of NO synthesis, presumably in endothelial cells, plays a significant role in pathophysiological alterations in vessels of rats with CHF.
Pulmonary vascular pressure effects by endothelin-1 in normoxia and chronic hypoxia: a longitudinal study
Authors: Tjen-A-Looi S. , Ekman R. , Osborn J. , Keith I.
Published: December 2017

The role of endothelin (ET)-1 in pulmonary arterial pressure (Ppa) homeostasis and hypoxia-induced pulmonary hypertension was examined. ET-1 was chronically infused (2 and 4 pmol.kg-1.min-1) into the pulmonary circulation of male Sprague-Dawley rats for 3, 7, and 14 days while they were exposed to normoxia or hypobaric hypoxia (inspired O2 fraction 10%). The role of endogenous ET was examined by infusion of ET antiserum (ET-AS; 0.25 and 0.5 microliter.rat-1.h-1; cross-reacting with ET-1, -2, and -3) or the ETA-receptor blocker BQ-123 (10 pmol.kg-1.min-1). ET-1 (4 pmol) increased Ppa at 3 and 7 days in normoxia and hypoxia and was ineffective at 14 days, probably from ETA-receptor downregulation. BQ-123 blunted the hypoxic Ppa rise at all times, confirming a role for ETA receptors. ET-AS (0.5 microliter) was mostly ineffective but exacerbated hypoxic Ppa at 14 days, in contrast to BQ-123, suggesting that a different ET receptor could be involved. ET-1 infusion (2 pmol) caused right ventricular hypertrophy (RVH) in normoxia and exacerbated RVH in hypoxia, whereas BQ-123 and ET-AS (0.25 microliter) reduced hypoxic RVH. In conclusion, endogenous ET-1 plays a role in hypoxia-induced pulmonary hypertension and RVH by augmenting the level of hypoxic response. ET-1 also affects hematocrit and may reduce blood levels of the vasodilator calcitonin gene-related peptide.
Effects of leukocyte capillary plugging in skeletal muscle ischemia-reperfusion injury
Authors: Harris A. G. , Skalak T. C.
Published: December 2017

The purpose of this study was to examine the relationship between increased capillary network resistance due to leukocyte capillary plugging and tissue injury following ischemia-reperfusion (I/R). After a 30-min complete ischemia in rat spinotrapezius muscle, the frequency and duration of leukocyte capillary plugging were measured throughout capillary networks and used to estimate the increase in network flow resistance for I/R alone, I/R with phalloidin (Pl), and I/R with both Pl and cytochalasin D. Propidium iodide (PI) was used to label nonviable muscle cell nuclei within the volume of tissue supplied by the capillary network, and counts were made before ischemia, immediately after reperfusion, and 1 h postreperfusion. For I/R alone and I/R + Pl there is a linear correlation between the increase in resistance (up to 29%) and the increase in the number of PI-positive nuclei during the reperfusion period. With both Pl and cytochalasin D present in the superfusate, the resistance increase was abolished and the amount of tissue damage during reperfusion was minimized. The results indicate that the increase in resistance is linearly related to the tissue damage and that a reduction of the leukocyte stiffness reduces the injury.
Diabetes rapidly induces contractile dysfunctions in isolated ventricular myocytes
Authors: Ren J. , Davidoff A. J.
Published: December 2017

To determine whether diabetes-induced cardiac dysfunction is due to contractile dysfunction at the single-cell level, mechanical properties and Ca2+ transients were evaluated in ventricular myocytes isolated from diabetic rats. Rats were made diabetic by injection with streptozotocin and killed either 4-6 days or 8 wk after treatment. Shortening and relengthening (twitch) properties were evaluated in isolated myocytes with a high-resolution (120-Hz) video-based edge-detection system during electrical stimulation between 0.1 and 5 Hz. A separate cohort of myocytes was loaded with fura 2 to assess intracellular Ga2+ transients. Long-term (8-wk) but not short-term (4- to 6-day) diabetes depressed peak twitch amplitude. Diabetes markedly prolonged both the contraction and relaxation phases from both diabetic models. Additionally, 35% of the long-term diabetic myocytes could not pace at 5 Hz, and 48% of the short-term diabetic myocytes developed a hypercontracture at that frequency. Intracellular Ca2+ measurements showed slower Ca(2+)-transient decays in myocytes from short-term diabetic rats. These data demonstrate that contractile dysfunction seen in the diabetic heart is due, in part, to abnormalities of the myocyte. Furthermore, these abnormalities are present after only 4-6 days of diabetes, suggesting a rapid alteration in the processes regulating myocyte shortening and relengthening, which likely include impaired Ca2+ sequestration or extrusion.
Characterizing ventricular mechanics and energetics following repeated coronary microembolization
Authors: Todaka K. , Leibowitz D. , Homma S. , Fisher P. E. , Derosa C. , Stennett R. , Packer M. , Burkhoff D.
Published: December 2017

Myocardial mechanics and energetics were investigated in an animal model of moderate chronic heart failure (CHF) created by repeated coronary microembolizations in six dogs. The final fractional area change was 34 +/- 4%. Hearts of these animals were isolated and cross-perfused, and balloons were placed in the left ventricle (LV). Chamber contractile state was markedly depressed in embolized hearts as assessed by the slope (Ees 2.74 +/- 0.49 vs. 4.00 +/- 1.18 mmHg/ml, P < 0.01) and volume axis intercept (V: 8.7 +/- 5.9 vs. 1.0 +/- 3.2 ml, P < 0.01) of end-systolic pressure-volume relation compared with a group of six normal dogs. The end-diastolic pressure-volume relation of embolized hearts was shifted to the right, indicating a dilation of the LV. However, systolic and diastolic stress strain relationships were similar in the two groups, suggesting that the average myocardial properties of the embolized hearts are similar to those of normal hearts. The relationship between oxygen consumption and pressure-volume area in embolized hearts had smaller intercept (2.98 +/- 0.44 vs 3.92 +/- 0.39 x 10(-2) ml O2.beat-1.100 g LV-1, P < 0.01) compared with the control group, with no change in the slope. These results contrast with previous findings in pacing CHF and serve as an important characterization of ventricular properties in this model of CHF from different etiology.
NO modulates autonomic effects on sinus discharge rate and AV nodal conduction in open-chest dogs
Authors: Elvan A. , Rubart M. , Zipes D. P.
Published: December 2017

The purpose of this study was to investigate the role of nitric oxide (NO) in mediating vagal and sympathetic modulation of spontaneous sinus cycle length (SCL) and atrioventricular (AV) nodal conduction time (A-H interval) in 62 open-chest mongrel dogs anesthetized with alpha-chloralose. Infusion of an NO synthase (NOS) inhibitor, NG-monomethyl-L-arginine (L-NMMA, 4 mg/ ml), into the sinus and AV nodal arteries attenuated significantly (P < 0.01) the negative chronotropic and dromotropic responses to vagal nerve stimulation (VS) and VS during ansae subclaviae stimulation (SS) or isoproterenol (Iso) infusion. Intravenous administration of L-arginine (100 mg/kg) reversed these responses toward control values, whereas D-arginine did not have a significant effect. L-NMMA significantly (P < 0.01) enhanced the effects of SS and Iso on SCL and A-H interval; L-arginine reversed these changes toward baseline. L-NMMA increased the minimum concentration of ACh needed to induce 50 or 100% prolongation of SCL or second-degree or complete AV block during concomitant Iso infusion. L-Arginine reversed these effects. NOS inhibition did not affect the direct cholinergic actions of ACh on SCL and A-H interval but enhanced adrenergic positive chronotropic and dromotropic effects. We conclude that NO plays a stimulatory role in mediating vagal neurotransmission and vagal modulation of sympathetic effects and an inhibitory role in mediating sympathetic neurotransmission.
Regional glucose uptake within hypoperfused swine myocardium as measured by positron emission tomography
Authors: McFalls E. O. , Baldwin D. , Palmer B. , Marx D. , Jaimes D. , Ward H. B.
Published: December 2017

Chronic myocardial ischemia and 2-[18F]fluoro-2-deoxy-D-glucose (FDG) uptake were studied with positron emission tomography in 12 swine instrumented with an external constrictor on the left anterior descending coronary artery (LAD). Serial changes in function (by echocardiography), blood flow (with H215O) and FDG were determined weekly. At 1 wk, function was normal and FDG uptake in the LAD and non-LAD regions was 0.43 +/- 0.12 and 0.45 +/- 0.11 mumol. min-1.g-1, respectively (not significant). At approximately 5 wk, LAD wall thickening decreased to 18 +/- 5 from 27 +/- 8% (P < 0.05), whereas LAD and non-LAD blood flows were 0.68 +/- 0.28 and 1.03 +/- 0.25 ml.min-1.g-1, respectively (P < 0.05). At that time, FDG uptake in LAD and non-LAD regions was 0.60 +/- 0.43 and 0.49 +/- 0.30 mumol.min-1.g-1, respectively (P < 0.05). By the use of transmural biopsies (n = 6), ATP and creatine phosphate in the LAD region were 3.62 +/- 0.73 and 5.91 +/- 1.44 mumol/g wet wt, respectively, and neither differed from values in remote regions. In this model of chronic ischemia, hypoperfused dysfunctional regions were characterized by enhanced glucose uptake and preserved bioenergetics. This supports the concept that the myocardium adapts to chronic ischemia.
Neuronal NOS-derived NO plays permissive role in cerebral blood flow response to hypercapnia
Authors: Okamoto H. , Hudetz A. G. , Roman R. J. , Bosnjak Z. J. , Kampine J. P.
Published: December 2017

The aim of the present study was to determine whether neuronal nitric oxide synthase (nNOS)-derived nitric oxide (NO) plays a permissive role in the regulation of cerebral blood flow (CBF) response to hypercapnia. To this end, we examined whether the administration of NO donors could reestablish the regional CBF (rCBF) response to hypercapnia after nNOS inhibition with 7-nitroindazole (7-NI). Rats were anesthetized with 1% halothane, and rCBF in the cortex was measured by laser-Doppler flowmetry. The administration of 7-NI (40 mg/kg ip) decreased resting rCBF by 17 +/- 5% (n = 6, P < 0.05) and attenuated the rCBF response to hypercapnia by 30 +/- 8% in comparison with the response seen in rats treated with the vehicle (peanut oil) alone. Intracerebroventricular administration of NO donors, sodium nitroprusside (SNP; n = 7) and (Z)-1-[N-methyl-N-[6(N-methylammoniohexyl)aminol]]diazen+ ++-1-ium-1,2-diolate (MAHMA NONOate; n = 6) in a dose of 0.1-1 nmol/min after 7-NI restored both resting rCBF to baseline and the vasodilatory response to hypercapnia. In contrast, intravenous infusion of SNP (0.05-0.5 nmol/min, n = 6) or intracerebroventricular administration of an NO-independent vasodilator, the stable prostaglandin I2 analog iloprost (0.01-0.1 nmol/min, n = 6), after 7-NI failed to restore the vasodilatory response to hypercapnia, despite the fact that it restored the resting rCBF to baseline. nNOS activity, assessed by the conversion of labeled arginine to citrulline, was inhibited by 70 +/- 7% after the administration of 7-NI. These findings confirm that the selective inhibition of nNOS decreases resting rCBF and attenuates the rCBF response of hypercapnia. They further indicate that the repletion of intraparenchymal NO allows the hypercapnic cerebrocortical vasodilation to occur. Therefore, it is suggested that the nNOS-derived NO plays a permissive role in the CBF response to hypercapnia.
Mechanical stimulation is not responsible for activation of gastrointestinal afferents during ischemia
Authors: Pan H. L. , Zeisse Z. B. , Longhurst J. C.
Published: December 2017

Abdominal ischemia reflexly excites the cardiovascular system through activation of visceral sympathetic afferents. Although a number of ischemic metabolites are known to stimulate sympathetic afferents, the contribution of mechanical stimulation to activation of afferents during abdominal ischemia remains uncertain. Thus the present study examined the role of changes in motility in activation of gastrointestinal afferents during ischemia. Single-unit activity of C fiber afferents located on the stomach, duodenum, jejunum, or colon was recorded from the right sympathetic chain of anesthetized cats during 15 min of ischemia. Intraluminal pressure, as a reflection of local mechanical activity, was measured by an open catheter placed in the lumen of the gastrointestinal tract. The results show that gastrointestinal motility was mainly inhibited during abdominal ischemia. Changes in intraluminal pressure did not correlate with afferent discharge activity during ischemia (r = -0.32, n = 10). Furthermore, discharge frequency of gastrointestinal afferents during ischemia was not altered significantly by topical application of 100 micrograms/ml of atropine (3.98 +/- 0.62 to 3.83 +/- 0.59 imp/s, n = 12), which profoundly inhibited local gastrointestinal motility. Collectively, these data indicate that gastrointestinal motility changes during abdominal ischemia do not contribute to activation of gastrointestinal sympathetic C fiber afferents.
Influence of hypoxia on endothelin-1 binding sites in neonatal porcine pulmonary vasculature
Authors: Noguchi Y. , Hislop A. A. , Haworth S. G.
Published: December 2017

Exposure to chronic hypobaric hypoxia in the newborn piglet causes pulmonary hypertension and structural abnormalities in the intrapulmonary arteries that resemble those seen in babies with pulmonary hypertension of the newborn. To investigate whether the density and subtype of endothelin (ET) receptors in intrapulmonary arteries were altered by exposure to chronic hypobaric hypoxia (50.8 kPa) and changed on recovery, (125)I-labeled ET-1 binding was studied using an in vitro autoradiographic technique on 67 piglets. Plasma ET was measured in 116 control, hypoxic, and recovery animals. In piglets exposed to hypoxia from birth, plasma ET was greater than normal for age (P < 0.05), and the binding density of ET-1 was increased in elastic arteries, muscular arteries, and veins due to an increase in the density of ET(A) binding (P < 0.05 for all vessel types). On recovery, plasma ET level became normal after 6 days. After 1 day of recovery, the binding density of ET-1 and ET(A) was normal in elastic arteries but was greater than normal in muscular arteries even after 6 days (P < 0.05). Exposure to hypoxia from 3 to 6 or from 14 to 17 days did not alter the plasma ET or the binding density in muscular arteries, but the density of binding of ET-1, ET(A), and ET(B) in elastic pulmonary arteries decreased (P < 0.05). On recovery, it returned to normal by 6 days. In summary, the increases in plasma ET and ET-1 and ET(A) binding density suggest a role for ET in the pathogenesis of hypoxic pulmonary hypertension in the newborn period. An initial normal period of adaptation is protective.
Role of kinin and renal ANG II blockade in acute effects of ACE inhibitors in low-renin hypertension
Authors: Naitoh M. , Suzuki H. , Arakawa K. , Matsumoto A. , Ichihara A. , Matsuda H. , Kubota E. , Murakami M. , Nakamoto H. , Saruta T.
Published: December 2017

In conscious deoxycorticosterone acetate (DOCA) salt-hypertensive dogs, the angiotensin-converting enzyme (ACE) inhibitors captopril and imidaprilat significantly decreased mean arterial pressure (MAP) and significantly increased urine flow rate, effective renal plasma flow (ERPF), glomerular filtration rate, and urinary sodium excretion. However, the angiotensin type 1 (AT1) receptor antagonist losartan caused a significant increase only in urinary sodium excretion without significant changes in MAP, urine flow rate, ERPF, and glomerular filtration rate. Simultaneous infusion of a bradykinin receptor antagonist inhibited the ACE inhibitor-induced reduction in MAP and increase in ERPF. DOCA salt treatment markedly suppressed plasma angiotensin II (ANG II) concentration (P < 0.001), although it decreased renal ANG II content only slightly (P < 0.05). Comparison of the expression of renal AT1 receptor mRNA in control kidneys with that in DOCA salt-hypertensive kidneys revealed no significant change. These results suggest that, in low-renin hypertension, inhibition of the relatively maintained ANG II production in the kidney participates in the natriuretic action of ACE inhibitors. However, hypotensive and other renal effects are mainly due to the action of bradykinin.
Purification, characterization, and localization of two ATP diphosphohydrolase isoforms in bovine heart
Authors: Beaudoin A. R. , Sevigny J. , Grondin G. , Daoud S. , Levesque F. P.
Published: December 2017

Two ATP diphosphohydrolase (ATPDase) isoforms have been purified from the bovine heart ventricle. The purification procedure includes the following steps: differential centrifugation, sucrose cushion centrifugation, solubilization with Triton X-100, DEAE agarose ion exchange, and Affi-Gel blue-Sepharose and concanavalin A (con A)-Sepharose chromatographies. The purified enzyme has an optimum pH of catalysis of 7.5 and requires Ca2+ or Mg2+. The apparent Michaelis constant of the enzyme, with ADP as the substrate, is 29 microM, and the apparent maximal velocity is 1.6 mumol.min-1.mg protein-1. Substrate specificity, heat-inactivation curves, and copurification of adenosinetriphosphatase (ATPase) and adenosinediphosphatase (ADPase) activities confirmed the identity of the purified enzyme as an ATPDase. In addition, polyacrylamide gel electrophoresis, under nondenaturing conditions, showed identical migration patterns for the protein involved in ATPase and ADPase activities. Western blot analysis, with an antibody that specifically recognizes the NH2-terminal sequence of pig pancreas ATPDase and specifically reacts with bovine and human ATPDases, showed cross-reactivity with the purified ATPDase isoforms from the bovine heart. Immunocytochemical localization in the ventricle produced strong reactions with the plasma membrane of Purkinje fiber cells and the majority of myocardial cells. Immunoreactivity was variable, producing a mosaic-like aspect. As expected, smooth muscle cells and endothelial cells of coronary vessels were highly reactive. This ectoenzyme could play a protective role against the potentially deleterious effects of extracellular ATP. In tandem with 5'-nucleotidase, it produces adenosine, a powerful vasodilator, especially in hypoxic or ischemic conditions that favor the release of ATP.