摘要:

The role of membrane potential-dependent and independent regulation of the intracellular free calcium concentration ([Ca2+]i) was assessed in the mesenteric small arteries of Wistar rats. [Ca2+]i was determined by Fura-2 fluorescence. Membrane potential measurements were made using intracellular microelectrodes. Depolarization with a high-potassium solution (K-PSS) elevated [Ca2+]i and induced contraction. Further addition of 10 µM noradrenaline (NA) did not elevate [Ca2+]i further but enhanced tone. Addition of calcium channel inhibitors (felodipine or D-600) inhibited the maintained rise in [Ca2+]i with K-PSS, but NA still elevated [Ca2+]i and force to about half the previous level. Further addition of either ryanodine or thapsigargin eliminated the rise in [Ca2+]i with NA, although 10–20% of the contraction remained. Simultaneous measurements of membrane potential, [Ca2+]i, and force during cumulative additions of NA or K-PSS in the absence of inhibitors showed similar relations between membrane potential and [Ca2+]i for each means of activation. The results indicate that membrane potential and [Ca2+]i are strongly correlated in mesenteric small arteries. A small part of the [Ca2+]i increase to NA can be attributed to release from intracellular stores. Membrane potential-independent calcium channels that are directly operated by adrenoceptors appear to play a minor role in the regulation of [Ca2+]i in these vesse

ISSN:1018-1172    

DOI:10.1159/000159059

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Transforming growth factor-β1 (TGF-β1) is a potent stimulator of proteoglycan (PG) synthesis by cultured smooth muscle cells. To test the hypothesis that TGF-β1 stimulates PG synthesis in whole artery wall we have investigated the effect of blocking endogenous TGF-β1 using an antisense S-oligonucleotide (ASO) directed against the first 7 codons for the N-terminal region of active TGF-β1. This sequence reduced TGF-β1 secretion by cultured endothelial cells by 40–55%. To determine the effect of the ASO on PG synthesis in whole vessel we chose the rat carotid artery (RCA) maintained in organ culture, a model in which we previously documented endothelial-dependent increases in PG snythesis over time in culture. We report here that the increases in PG in the inner layers of the vessel wall are matched by similar increases in TGF-β1 mRNA. To test for the effect of ASO on PG synthesis, small segments of RCA, maintained in organ culture (Medium 199, supplemented with 1 % FCS), were exposed on day 6 to either control media, antisense TGF-β1, sense TGF-β1, or a non-sense sequence at 5, 10 and 20 µM concentrations. Following 24 h exposure to the oligonucleotides, cultures were labelled for a further 24 h with [3H]glucosamine and processed for autoradiography. Antisense TGF-β1 at 10 and 20 µM produced a 60% reduction in PG synthesis in the endothelium and adjacent first layer of the media. The remaining medial layers and adventitia were not affected by the ASO. These results are consistent with the hypothesis that TGF- β1 plays a role in controlling PG synthesis in the inner wall where l

ISSN:1018-1172    

DOI:10.1159/000159060

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Cyclic GMP-dependent protein kinase (cGMP kinase) is the major receptor protein for cGMP in vascular smooth muscle. Vascular smooth muscle cells (VSMC) isolated from the rat aorta express type I cGMP kinase at high levels, but expression decreases markedly upon passage of the cells. In primary or early passage, the expression of cGMP kinase is lowest when cells are plated at low density as assessed by immunological and Northern analyses. Expression increases at confluence and is maintained in postconfluent cultures. With repeated passaging, however, the levels of cGMP kinase decrease even in confluent and postconfluent cultures so that after several passages enzyme levels are undetectable. The decrease in expression in passaged cells is not due to exposure to serum-derived growth factors, but rather on the repeated exposure of cells to conditions in which cell density is reduced (i.e., subculturing). These results indicate that aortic VSMC grown at low density or those repetitively passaged have reduced expression of cGMP kinase, and thus may not represent appropriate cultures with which to investigate the role of nitric oxide and cGMP in VSMC function.

ISSN:1018-1172    

DOI:10.1159/000159061

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Coronary resistance arteriolar diameter importantly regulates myocardial blood flow, and is influenced by circulating neurohumoral agents. Angiotensin II (A-II) is a circulating polypeptide that is chronically elevated in heart failure and serves as a potent peripheral vasoconstrictor agent. However, its effects on isolated coronary resistance arterioles is relatively unknown. We compared the vasomotor effects of A-II on coronary epicardial and resistance arterioles in vitro from both the canine and porcine heart in order to determine the effects of A-II in different vascular beds and species. Epicardial rings were studied under isometric recording conditions, while resistance arterioles (50–150 µm) were studied in vitro using a video imaging system to record diameter. A-II, whether applied to passively distended or preconstricted porcine resistance arterioles, did not cause vasoconstriction when applied as a bolus or as cumulative doses. In preconstricted canine resistance arterioles, A-II elicited dose-dependent vasodilation (EC50 = 0.2 nM). In passively distended canine arterioles, high concentrations of A-II (0.1 µM)applied as a bolus elicited transient vasoconstriction in 28% of the vessels studied. In large epicardial rings, A-II was a weak vasoconstrictor, with greater potency in canine arteries compared to porcine arteries. In canine arteries, vasoconstriction to A-II was augmented after incubation with indomethacin. In contrast to the findings in canine arteries, the A-II vasoconstrictor response in porcine coronary arteries was decreased after incubation with indomethacin or removal of the endothelium. Thus, A-II elicits the release of a vasodilator prostanoid in epicardial canine coronary arteries and a vasoconstrictor prostanoid in porcine vessels which modulate the vasomotor action of A-II. Receptor binding assays to compare A-II receptors in resistance arterioles and epicardial arteries showed that porcine arterioles possessed significantly more membrane receptors for A-II than porcine epicardial vessels, whereas there was no difference between canine epicardial and arteriolar A-II receptor densities. In conclusion, A-II exerted complex actions on both large epicardial vessels and resistance arterioles, with significant differences between species. A-II was a weak vasoconstrictor in both porcine and canine epicardial vessels. The net vasomotor response was the result of interactions between vasoactive prostanoids and direct smooth muscle vasoconstrictor effects on the coronary artery. A-II was a potent vasodilator of canine, but not porcine, resistance arterioles, and in some vessels elicited transient vasoconstriction at high A-II concentrations. Despite the presence of A-II receptors, in porcine resistance arterioles A-II had no vasomotor effects in either passively distended or preconstricted arterio

ISSN:1018-1172    

DOI:10.1159/000159062

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Epidemiological studies have indicated that hypertension enhances the development of atherosclerosis in patients with lipid disorders. However, it was still unclear whether this promoting effect resulted only from hemodynamic changes or whether part of it was mediated by humoral or neurogenic factors independent of blood pressure alteration. The aim of this study was to determine whether mineralocorticoids, which are known to be involved in the pathogenesis of hypertension, could be implicated in the atherosclerotic process independent of pressure changes. For this purpose, the effect of deoxycorticosterone (DOCA, 200 mg/kg s.c.) on aortic atherosclerosis was studied in Watanabe heritable hyperlipidemic (WHHL) rabbits in comparison with New Zealand rabbits. After 4 weeks of treatment, DOCA significantly increased the size of atherosclerotic lesions in the arch and thoracic aorta (+115%) in parallel with the aortic cholesterol ester content (+83%). The vascular free cholesterol and triglyceride content remained unchanged on DOCA treatment, as were arterial pressure and plasma cholesterol levels. None of these effects was observed in New Zealand rabbits. DOCA did not accentuate the alteration of endothelial function usually found in WHHL rabbits. The sensitivity to serotonin was not altered, but the maximal contraction to this agonist was decreased in both strains by mineralocorticoid treatment.

ISSN:1018-1172    

DOI:10.1159/000159063

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Studies on the possible causal relationship between the Ca2+ channel current density in the vascular muscle cell (VMC) and increases in blood pressure were extended by a comparison of stroke-prone spontaneously hypertensive rats (SP-SHR) with N/nih outbred normotensive rats. Maximal amplitudes of both L-type and T-type Ca2+ channel currents were significantly increased in SP-SHR without a difference in cell capacitance. SP-SHR peak current amplitudes in 20 mM Ba2+ averaged 446 ± 64 pA while N/nih averaged 156 ± 25 pA (clearly separated statistically). Both L-type and T-type Ba2+ currents (IBa) were significantly increased in SP-SHR, shown also by peak current frequency distributions. There was a significant shift to the left of both activation (7 mV) and inactivation (15 mV) current-voltage (I-V) plots. SP-SHR IBa recovery from inactivation was significantly slower (103 versus 61 ms) than in N/nih VMC. The increases in SP-SHR IBa amplitude under maximized conditions correlated with increases in blood pressure. Together with earlier observations of increased vascular muscle Ca2+ current density coexistent with blood pressure elevation in Kyoto-Wistar SHR, these data provide evidence for altered function of Ca2+ channels as a fundamental component of hypertension. Since the Ca2+ channel alterations exist in venous VMCs of newborn SP-SHR rats (in a low pressure blood vessel and at a time when increased Ca2+ current density could not be an effect of increased blood pressure), our results add to the growing evidence of Ca2+ channel abnormalities as a cause of genetic hypertensio

ISSN:1018-1172    

DOI:10.1159/000159064

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000159065

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000159066

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000159067

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000159058

出版商:S. Karger AG    

年代:1994

数据来源: Karger