摘要:

Synthetic atrial natriuretic factor (ANF) has been found to be a potent relaxant of isolated vascular preparations. ANF is more effective in relaxing agonist-induced versus depolarized contractile events and the relaxation efficacy appears inversely related to the level of contractile preload. The vasorelaxation to ANF is associated with elevations of cyclic GMP via an activation of the particulate form of guanylate cyclase. Both species and regional-vascular differences exist, in vitro as well as in vivo, in the vasorelaxation response to ANF which may reflect an altered distribution of high affinity receptors and/or different states of active vascular tone of the particular preparation.

ISSN:1018-1172    

DOI:10.1159/000158685

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The role of endothelial cells in modulating the vascular smooth muscle tone in aging and hypertension was examined. Results from in vitro pharmacological studies indicate that vasodilations of rat arteries induced by several dilator agents, such as nitrovasodilators, decrease with advancing age and experimental hypertension. These diminished dilator responses to nitrovasodilators however were not observed in arteries with endothelial cells removed. Furthermore, 8-bromo-cGMP-induced relaxations were not different between arteries with and without endothelial cells and were not affected by hypertension. It appears that the diminished vasodilator responses in aging and hypertension is not initially due to defects in vascular smooth muscle but rather due to an altered modulatory function of the endothelial cells. At different ages and under different pathological conditions, such as hypertension, the ratio of production and/or activities of endothelium-derived relaxing factors and endothelium-derived constrictor factors may vary, and therefore directly or indirectly affect the production of cGMP and smooth muscle tone.

ISSN:1018-1172    

DOI:10.1159/000158686

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Norepinephrine concentrations in excess of 10–4M are achieved at the post-junctional membrane of the adrenergic synaptic cleft in resistance arteries at least for short periods of time. These concentrations are greater than the threshold of low affinity non-α-adrenoceptors-’extraceptors’, that respond to norepinephrine and would be sufficient to overcome the blockade by α-adrenoceptor antagonists. The relationship of such activity to the excitatory junction potential and the relevance of this to contraction in vivo remains a matter of con

ISSN:1018-1172    

DOI:10.1159/000158687

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Endothelium-dependent contractions of isolated veins can be induced with arachidonic acid and thrombin. Anoxia causes endothelium-dependent contractions in a variety of isolated arteries and veins. Rapid stretch and acetylcholine contract cerebral arteries with, but not those without endothelium. Acetylcholine (and serotonin) cause endothelium-dependent contractions in the aorta of the spontaneously hypertensive, but not that of the normotensive rat.

ISSN:1018-1172    

DOI:10.1159/000158688

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

In the perfused mesenteric arterial vasculature of the rabbit, vasodilation by acetylcholine (ACh) was almost completely blocked after a 15-min perfusion of the vasculature with 0.2% collagenase, an enzyme capable of removing endothelial cells. In the perfused mesenteric arterial vasculature of the rat, vasodilation by ACh was markedly, though not completely, inhibited by hemoglobin (10 µM), an agent which can inactivate endothelium-derived relaxing factor (EDRF). These results suggest that a major component of vasodilation of mesenteric resistance vessels in rabbit and rat by ACh is mediated by EDRF

ISSN:1018-1172    

DOI:10.1159/000158689

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Uridine triphosphate (UTP) and uridine diphosphate (UDP) are present in platelets, probably linked to storage organelles. In several animal species, UTP is a powerful constrictor of cerebral arteries, with no detectable dilatory component, which was confirmed in the present study. When testing the vasomotor effects of UTP and UDP in precontracted isolated segments of human pial arteries it was found that these nucleotides were powerful, transient dilators in the concentration range 10–7–10–5 Min the majority of vessels studied. At higher doses a contractile response supervened. Uridine monophosphate and uridine were without effect. Removal of the vessel endothelium mechanically or by perfusion with Triton abolished the dilatory response, and now the contraction appeared already at 3 × 10–6 M The present findings add UTP and UDP among the group of endothelium-linked biogenic vasodilators. This may be of pathophysiological importance in the maintenance of an adequate brain circulation in disorders involving platelet dys

ISSN:1018-1172    

DOI:10.1159/000158690

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Dual control of local blood flow by purines is described: (1) adenosine 5’-triphosphate (ATP) released as a cotransmitter with noradrenaline from perivascular sympathetic nerves acts on P2X-purinoceptors on smooth muscle cells to produce vasoconstriction; (2) ATP released from endothelial cells during hypoxia (and ADP released from aggregating platelets) acts on P2Y-purinoceptors on endothelial cells which results in production of endothelium-derived relaxing factor and subsequent vasodilatation. It is suggested that the endothelial-mediated vasodilatation is a pathophysiological mechanism to protect the host tissue (e.g. brain or heart) from damage produced by hypoxia following ischaemia. The ATP released from the endothelial cells is rapidly broken down to adenosine which augments this protective mechanism by acting directly on P1-purinoceptors on vascular smooth muscle to produce a longer lasting component of vasodilatation and on perivascular sympathetic nerve terminals to inhibit release of excitatory neurotransmitters. The possibility that impairment of normal endothelial-mediated responses in atherosclerosis and hypertension can lead to local vasospasm is considere

ISSN:1018-1172    

DOI:10.1159/000158691

出版商:S. Karger AG    

年代:1987

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158692

出版商:S. Karger AG    

年代:1987

数据来源: Karger