摘要:

We have studied contractile responses to norepinephrine (NE) and K+ of isolated rabbit ear arteries and veins in an effort to determine how α -adrenoceptor affinity and smooth muscle contractility affect responsiveness at different temperatures. Arteries have predominantly α1-adrenoceptors and veins have predominantly receptors of the α 2-type. We obtained dose-response curves to NE at 9, 16, 23, 30, 37 and 42 °C in the absence and presence of the irreversible α -adrenoceptor blocker phenoxybenzamine (POB). In both vessels, affinity of the α -adrenoceptors was determined by comparing equieffective doses of NE before and after blockade of the receptors. In other experiments, we obtained contractions to 80 mMKCl at the same temperatures. Affinity of the ear arterial α1-receptors was maximal at 23 °C, while affinity of ear venous α2-receptors increased linearly with cooling to 9 °C. Responses to K+ in both vessels decreased with cooling. Taken together, the changes in receptor affinity and response to K+ may explain the shape of curves relating contractile strength to te

ISSN:1018-1172    

DOI:10.1159/000158767

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

The spontaneous rupture of the internal elastic lamina (IEL) in various arteries occurs to different extents in different rat strains. We have quantified this phenomenon in the caudal and renal arteries and abdominal aorta in two normotensive inbred strains: the Brown Norway (BN) and Long Evans (LE) strains. At 5 weeks of age, BN rats of both sexes exhibited small numbers of interruptions in the IEL of the caudal artery, whereas LE rats did not. Postpubertal male and female BN rats presented large numbers of IEL interruptions in the caudal artery and significant numbers in the renal artery and abdominal aorta, whereas LE rats showed few in the caudal artery and none in the other arteries. Treatment with β -aminopropionitrile (BAPN, an inhibitor of lysyl oxidase, the enzyme involved in the formation of cross-links in elastin and collagen) increased the formation of IEL ruptures in both strains in the caudal and renal artery and in the abdominal aorta in BN rats, but not in the abdominal aorta of LE rats. Apart from IEL ruptures, which were more prevalent in BN rats, no differences were observed in the ultrastructure of the aortic elastic fibers between the two strains, either in controls or in BAPN-treated rats. When male rats of both strains were made hypertensive by unilateral nephrectomy and administration of deoxycorticosterone and salt, mortality was more precocious in the BN strain although blood pressure was significantly higher in the BN strain at only one time point. The incidence of cerebrovascular hemorrhage was 48% in BN rats and 0% in LE rats. Hypertension increased the formation of ruptures in the IEL in some arteries – to a greater extent in the BN than in the LE rats. These results raise the possibility that the propensity to spontaneous rupture of the IEL, which is in part genetically determined, may reflect a latent form of vascular fragility which becomes significant in hypertension, resulting in poor survival and susceptibility to cerebrovascular acciden

ISSN:1018-1172    

DOI:10.1159/000158768

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

Experiments were designed to determine the mechanism by which electrical stimulation causes tetrodotoxin-insensitive relaxation in isolated arteries. Rings of left anterior descending coronary arteries of dogs, pigs and calves were suspended in organ chambers between platinum electrodes. Experiments were performed after treatment with phenoxybenzamine and in the presence of propranolol. Calcium-free solution and calcium antagonists reduced the relaxation. Chemical denervation with 6-hydroxydopamine reduced the relaxation induced by electrical stimulation; in the presence of pargyline, the inhibitor of monoamine oxidase, it was virtually abolished. The nonselective dopaminergic antagonist droperidol and the selective DA1-dopaminergic antagonist SKF R83566 caused a concentration-dependent inhibition of the relaxation; the DA2-dopaminergic antagonist domperidone was ineffective. High concentrations of dopamine induced relaxation of the coronary smooth muscle; the relaxation was inhibited by SKF R83566 but not by droperidol. These results suggest that electrical stimulation causes relaxation by liberating an endogenous vasodilator substance, which acts on DA1-dopaminergic receptors of the coronary smooth muscle.

ISSN:1018-1172    

DOI:10.1159/000158769

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

Substance P (SP) and bradykinin (BK) relax and hyperpolarize smooth muscles of pig coronary arteries in an endothelium-dependent manner. We investigated the effect of both peptides on the membrane potential of endothelial cells in culture. The membrane potential of pig coronary artery endothelial cells in primary culture was -44 mV. SP and BK hyperpolarized it transiently by 23 mV. These hyperpolarizations were dependent on the potassium gradient across the cellular membrane. They had similar time courses as the SP and BK endothelium-dependent hyperpolarizations already observed in smooth muscles.

ISSN:1018-1172    

DOI:10.1159/000158770

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

The reactivities of porcine resistance-sized arteries (270 µm o.d.) and conductance coronary arteries (4.2 mm o.d.) were compared in the presence of a functional and morphologically intact endothelium using a pressurized in vitro preparation. In resistance vessels, acetylcholine (ACh) produced maximal diameter reductions of 42 % and the EC50 was 0.19 µM. Constrictions to histamine and prostaglandin F2α (PGF2«), however, were either absent or minimal. In contrast, maximum diameter constrictions of conductance vessels were 19, 33 and 22% in response to ACh, histamine and PGF2α, respectively. Corresponding EC50 values were 0.58, 2.8 and 2.9µM. The significant differences in reactivity between resistance and conductance arteries underscore the potential importance of regional specialization in the coronary blood flow regul

ISSN:1018-1172    

DOI:10.1159/000158771

出版商:S. Karger AG    

年代:1989

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158772

出版商:S. Karger AG    

年代:1989

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158773

出版商:S. Karger AG    

年代:1989

数据来源: Karger