Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The endothelium is increasingly recognized as a modulator of vascular tone, and evidence also is accumulating for an important role of the endothelium in humans in vivo. Endothelial release of prostacylin appears to regulate hyperemic blood flow after ischemia and muscle exercise, and the potent vasodilating properties of endothelium-derived relaxing factor (EDRF) are well established. Tonic release of EDRF plays an important role in the regulation of vascular tone in normal subjects, and a reduction of EDRF release in response to muscarinergic stimulation has been described in subjects with uncomplicated hypertension and also in hyperlipidemic patients. These observations point toward an early disturbance of endothelial function in disorders known as risk factors for the development of atherosclerosis. Furthermore, altered EDRF release and responsiveness to stimuli may be involved in the disturbed regulation of peripheral vascular tone in congestive heart failure. The physiological role of the vasoconstricting peptide endothelin-1 is not yet defined, but the study of the vascular actions of the peptide in humans has shown a vasodilating effect (for low dosages or when the vasconstricting effects are blocked), as well as a marked and long-lasting vasoconstricting effect. Although the mechanisms leading to vasodilation are not clear in humans, endothelin-1-induced vasoconstriction appears to be completely dependent on the activity of voltage-operated calcium channels and can be blocked by organic calcium antagonists but not by nitrovasodilators or EDRF. Further clarification of the role of the endothelium will provide a better understanding of circulatory physiology and pathophysiology and eventually may lead to the development of new therapeutic modalities.
Hypertension 1991 Oct
PMID:Endothelial function in humans. Studies of forearm resistance vessels. 191 1

Endothelial cells may produce and release vasoconstrictor substances in response to a number of agents and physical stimuli. In this brief review, current understanding of the mechanisms of endothelium-dependent contractions will be discussed. Cyclooxygenase products of arachidonic acid metabolism including thromboxane A2, prostaglandin H2, superoxide anions, vasoconstrictor peptide endothelin-1, and unidentified factor released from endothelium by hypoxia may mediate these contractions. The physiological role of endothelium-dependent contractions in regulation of the cardiovascular system is unknown. Existing evidence supports the concept that contracting factors may become important regulators of vascular tone under pathological conditions. We speculated about the possible importance of endothelium-dependent contractions for venous graft function, development of vasospasm, increased vascular resistance in hypertension, and vascular complications in diabetes.
Hypertension 1991 Nov
PMID:Endothelium-derived vasoactive factors: II. Endothelium-dependent contraction. 193 91

As a source of several vasoactive factors, the endothelium takes part in the regulation of vascular tone. The most important endothelium-derived vasoactive substances are nitric oxide, prostacyclin, endothelin-1 and contracting factors requiring the activity of cyclooxygenase. The endothelium is an obvious target organ of cardiovascular risk factors. Accordingly, functional alterations do occur with aging, hypertension, and lipids. All three conditions are associated with a decreased basal and stimulated release of endothelium-derived nitric oxide. On the other hand, the release of endothelin-1 appears to increase with age, while the sensitivity to the peptide markedly decreases under the same conditions. In the spontaneously hypertensive rat, acetylcholine and stretch evoke the release of cyclooxygenase-dependent endothelium-derived contracting factor, most likely prostaglandin H2. The sensitivity and circulating levels of endothelin-1, on the other hand, are reduced in this experimental model of hypertension. In the porcine coronary circulation, oxidized low-density lipoproteins selectively reduce endothelium-dependent relaxations to aggregating platelets, serotonin, and thrombin which are mediated by nitric oxide. The alterations of endothelial function occurring with aging, hypertension, and hyperlipidemia may have important clinical implications for the pathogenesis of cardiovascular disease.
 ...
PMID:Endothelium-dependent control of vascular tone: effects of age, hypertension and lipids. 195 6

It has been shown that endothelin-1 (ET-1) binding sites exist in the central nervous system and that the injection of intracerebroventricular ET-1 induces a pressor response. Therefore, we determined the neurohormonal and cardiovascular responses to intracerebroventricular ET-1 (25 pmol/kg) in conscious rabbits with chronically instrumented electrodes on the renal sympathetic nerve. Intracerebroventricular ET-1 provoked a prompt increase in arterial pressure and in renal sympathetic nerve activity within 5 minutes, and peak values were obtained at 20 and 40 minutes, respectively. Plasma epinephrine and norepinephrine reached peak values at 5-20 minutes. Plasma vasopressin and plasma glucose levels also increased significantly, but plasma osmolality, hematocrit, and serum sodium and potassium concentrations did not show any changes. Arterial blood gas analysis showed respiratory alkalosis. However, pretreatment with intravenous pentolinium (5 mg/kg), a ganglion blocking agent, abolished these neurohormonal and cardiovascular responses. Conversely, the same dose of intravenous ET-1 (25 pmol/kg) as that used in the intracerebroventricular experiment failed to cause any cardiovascular or renal sympathetic nerve responses. These results suggest that intracerebroventricular ET-1 acts in the central nervous system and causes a pressor response mainly through the enhancement of sympathoadrenal outflow.
Hypertension 1991 Jun
PMID:Central effect of endothelin on neurohormonal responses in conscious rabbits. 204 64

Endothelins are endothelial cell-derived peptides with potent vasoconstrictor properties. We investigated the actions of porcine/human endothelin-1 (ET-1) on the microvasculature of the guinea pig lung perfused at constant flow with Ringers-albumin. We measured the perfusion pressure, distribution of pulmonary vascular resistance (using the double occlusion method), lung weight change, and the pulmonary capillary filtration coefficient. At concentrations of greater than or equal to 10(-10) M, ET-1 produced dose-dependent increases in mean pulmonary artery pressure (EC50, approximately 10(-9.5) M), which were rapid in onset and biphasic (first phase peaking at 1-2 minutes; second phase peaking at 10-15 minutes) up to 60 minutes of the perfusion period. The vasoconstrictor response was sustained for the 60-minute perfusion period. The pulmonary vasoconstriction was inhibited by pretreatment with indomethacin (10(-5) M), the thromboxane A2 receptor antagonist SQ-29,548 (4 x 10(-6) M), or papaverine (10(-5) M). Nifedipine (10(-5) or 10(-7) M) had no effect on the first phase but prevented the second phase of the vasoconstriction. The vasoconstriction was primarily the result of a 10-fold increase in pulmonary venous resistance. Pulmonary edema developed after ET-1 challenge because of the venoconstriction and the resultant pulmonary capillary hypertension. However, the pulmonary capillary filtration coefficient was unchanged, indicating that pulmonary vascular permeability did not increase. ET-1 also had no effect on transendothelial 125I-albumin flux. The results indicate that ET-1 is a potent thromboxane-dependent venoconstrictor in the guinea pig lung.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Mechanism of endothelin-1-induced pulmonary vasoconstriction. 205 31

It is suggested that endothelin-1 (ET-1), a potent vasoconstrictor peptide, is involved in the pathogenesis of cerebral vasospasm following subarachnoid hemorrhage (SAH). We examined the effects of intracisternal administration of big ET-1 on the cerebral arteries in the absence or presence of pretreatment with phosphoramidon, an inhibitor of ET converting enzyme, in anesthetized dogs. After intracisternal administration of big ET-1 (10 micrograms/dog), the caliber of the basilar artery on the angiogram was decreased to about 59% of the control. This was accompanied by a marked increase in immunoreactive ET in the cerebrospinal fluid. Systemic arterial pressure was markedly elevated following big ET-1 injection. All changes induced by big ET-1 were effectively prevented with phosphoramidon. These data suggest that intracisternally administered big ET-1 is converted to ET-1 and that the generated ET-1 produces cerebral vasospasm and hypertension. A phosphoramidon-sensitive metalloproteinase appears to contribute to this conversion.
 ...
PMID:Phosphoramidon inhibits the conversion of intracisternally administered big endothelin-1 to endothelin-1. 206 64

In this study we have investigated whether the vascular smooth muscle of a large capacitance artery of spontaneously hypertensive rats (SHR) is hyperresponsive to endothelin-1 and whether the arterial responsiveness to endothelin-1 is affected by aging. Isometric contractions of spirally cut aortic strips from SHR of 11, 22, 33 and 44 weeks of age and from age-matched WKY were measured in parallel. The vessels from SHR did not exhibit a greater responsiveness to endothelin-1 than those from WKY. No difference of responsiveness to the peptide was found among the arteries isolated from WKY of different ages. In contrast, a progressive decrease of responsiveness to endothelin-1 with aging was observed in SHR. This finding seems to be specific for endothelin-1, since the responsiveness to norepinephrine was unchanged. The significant decrease of aortic responsiveness in SHR with aging might be due to chronic hypertension and indicate desensitization to endothelin-1. The latter might be related to chronic in vivo hyperproduction of endothelin, either genetically determined or related to the hypertension-induced endothelial damage.
 ...
PMID:In vitro vascular reactivity to endothelin: a comparison between young and old normotensive and hypertensive rats. 208 74

1. The regional haemodynamic effects of bolus doses (4 and 40 pmol) and infusions (12 and 120 pmol h-1) of endothelin-1 and endothelin-3 were assessed in conscious, Long Evans and Brattleboro (i.e. vasopressin-deficient) rats, chronically-instrumented with pulsed Doppler flow probes. 2. In both strains of rat the lower bolus dose of endothelin-1 caused only a slight pressor effect, but there were marked renal and mesenteric vasoconstrictions and hindquarters vasodilatation. 3. The lower bolus dose of endothelin-3 did not affect blood pressure significantly, although the changes in regional haemodynamics were qualitatively similar to those seen following endothelin-1 in Long Evans and Brattleboro rats. 4. The higher dose of endothelin-1 caused an initial hypotension accompanied by substantial hindquarters vasodilatations in Long Evans and Brattleboro rats. Subsequently, in both strains, there was a rise in blood pressure accompanied by renal, mesenteric and hindquarters vasoconstrictions. 5. The higher bolus dose of endothelin-3 caused initial hypotension and hindquarters vasodilatation similar to those seen with endothelin-1. However, the subsequent pressor effect was less with endothelin-3, as was the renal vasoconstriction, and it did not cause any increase in hindquarters vascular resistance. 6. Infusion of endothelin-1 at the lower rate (12 pmol h-1) caused renal and mesenteric vasoconstrictions in both strains of rat, whereas endothelin-3 at this rate caused only mesenteric vasoconstriction. 7. Infusion of endothelin-1 at the higher rate (120 pmol h-1) caused progressive hypertension and vasoconstrictions in all three vascular beds studied; these were similar in both strains of rat. Endothelin-3 had a smaller pressor effect and a lesser constrictor action on the renal and mesenteric vascular beds; it did not constrict the hindquarters vascular bed. 8. These results show, that in conscious Long Evans and Brattleboro rats, the initial depressor effects of the higher bolus doses of endothelin-1 and -3 were similar, and, hence, not influenced by the absence of endogenous vasopressin. Endothelin-1 and -3 appear equipotent in their initial hyperaemic vasodilator effects in the hindquarters vasculature in both strains, making it unlikely that this effect is dependent on the release of atrial natriuretic peptide (ANP), since ANP does not cause significant increases in hindquarters blood flow in Brattleboro rats. The greater delayed pressor effect of endothelin-1 is associated with its more marked vasoconstrictor effects on renal and mesenteric vascular beds and is accentuated, relative to endothelin-3, by the lack of a constrictor effect of endothelin-3 in the hindquarters vasculature.
 ...
PMID:Regional haemodynamic effects of endothelin-1 and endothelin-3 in conscious Long Evans and Brattleboro rats. 213 84

125I-labelled endothelin-1 was used to identify specific high affinity endothelin-1 binding sites in left ventricular and brain membranes harvested from female age-matched normotensive Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). Relative to results obtained for brain membranes from normotensive rats, brain membranes from hypertensive rats exhibited an increase in 125I-endothelin-1 binding site density (P less than 0.02). In left ventricular membranes from the hypertensive rats 125I-endothelin-1 binding site density was reduced (P less than 0.02), relative to the density in ventricular membranes of normotensive rats. These results indicate that hypertension may have an organ specific effect on 125I-endothelin-1 binding site density.
 ...
PMID:125I-endothelin-1 binding to brain and cardiac membranes from normotensive and spontaneously hypertensive rats. 215 10

To investigate the possible involvement of endothelin-1 (ET-1), an endothelium-derived potent vasoconstrictor peptide, in the pathophysiology of hypertension, plasma ET-1 levels in 15-week-old spontaneously hypertensive rats (SHR) and DOCA-salt hypertensive rats were measured with a sandwich-type enzyme immunoassay. The vasocontractile effect of ET-1 in aortic helical preparations was significantly more sensitive in DOCA-salt hypertensive rats than in control sham-operated rats, but plasma levels of ET-1 did not differ between them. Plasma ET-1 levels in genetically hypertensive rats (SHR and stroke-prone SHR) were significantly lower than those in age-matched normotensive Wistar-Kyoto (WKY) rats. The plasma concentrations of big ET-1, a precursor of ET-1, in both SHR and SHR-SP were significantly lower than those of WKY, suggesting that the production of ET-1 is decreased in rats of genetic hypertension. Although the vascular reactivity to ET-1 increased in both DOCA-salt hypertensive and genetically hypertensive rats, present findings of the plasma ET-1 levels suggest that the role of ET-1 in the vascular control system may be different in DOCA-salt hypertensive rats and genetically hypertensive rats.
 ...
PMID:Plasma concentrations of endothelin-1 in spontaneously hypertensive rats and DOCA-salt hypertensive rats. 218 29


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>