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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Renovascular hypertension is relieved by percutaneous transluminal renal angioplasty. In four patients with renovascular hypertension, platelet-activating factor (PAF) was found to be released into the ipsilateral renal venous blood after percutaneous transluminal renal angioplasty, but was not found in the contralateral renal venous blood following this procedure. Anti-platelet-activating factor with a lipid-like property was also found, and its polarity was slightly lower than that of PAF judging by its behavior on thin layer chromatography. Anti-platelet-activating factor completely blocked the aggregation of rabbit platelets induced by PAF, ADP or arachidonic acid. These results indicate that PAF and anti-platelet-activating factor are released into renal venous blood following percutaneous transluminal renal angioplasty in patients with renovascular hypertension.
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PMID:Endogenous platelet-activating factor and anti-platelet-activating factor in patients with renovascular hypertension. 296 84

Arterial hypertension is considered a major risk factor in atherosclerosis in the pathogenesis of which platelet activity plays a fundamental role. However the data in the literature on platelet function in arterial hypertension do not always agree. The present study was conducted on whole blood, using the impedance metering technique to assess platelet aggregation induced by ADP (10 pg) and collagen (2 mg/ml) in 15 patients with uncomplicated essential hypertension and 25 healthy controls. Analysis of the data shows a statistically significant difference between the aggregation curves of the hypertensive and the healthy subjects with excessive platelet aggregation in those suffering from uncomplicated arterial hypertension.
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PMID:[Platelet aggregation in whole blood with the impedance method in subjects with non-complicated essential arterial hypertension]. 296 26

The mechanism of the acute fall of BP following percutaneous transluminal renal angioplasty (PTRA) was studied in four patients with renovascular hypertension caused by fibromuscular dysplasia. One hour after PTRA, systemic blood pressure and plasma renin activity in the ipsilateral renal venous blood decreased significantly (P less than 0.05), but the plasma noradrenaline level in ipsilateral renal venous blood increased significantly (P less than 0.05). At the same time, a platelet-activating factor (PAF) and an unidentified factor that inhibited the aggregation of rabbit platelets induced by PAF, arachidonic acid or ADP were detected in the ipsilateral renal venous blood, but were not found in the contralateral renal venous blood. Plasma noradrenaline level in cubital venous blood decreased significantly (P less than 0.05) after 24 hours as compared with that before PTRA and BP also maintained the normal level. These results suggest that the reduction in plasma renin activity is associated with the acute reduction in BP following PTRA. PAF and an unidentified factor blocking the aggregation of platelets may be involved in ipsilateral renal venous blood following PTRA in patients with renovascular hypertension. The reduction in plasma noradrenaline level is an additional mechanism involved in maintaining normal BP following PTRA in the late stage.
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PMID:Platelet-activating factor and anti-platelet-aggregating factor in acute reduction of blood pressure following percutaneous transluminal renal angioplasty in patients with renovascular hypertension. 297 5

Dual control of local blood flow by purines is described: 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; 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 considered.
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PMID:Local control of blood pressure by purines. 303 84

The influence of some oral hypoglycaemic sulfonyl ureas on PGI2 release by the rat thoracic aorta in vitro was examined using reversed phase HPLC. The column (Micro Pack MCH-10) (30 cm X 4 mm) was eluted using the solvent mixture:acetonitrile:glacial acetic acid:water (23:0.1:76.9v/v/v). Preincubation of the aortae with the sulfonyl ureas (15 microM) enhanced PGI2 release. The control release (measured as 6-oxo-PGF1 alpha) was 1.15 +/- 0.1 ng/mg wet weight. This was significantly increased to 2.30 +/- 0.20, 2.50 +/- 0.30, 2.90 +/- 0.25, 2.10 +/- 0.20 and 2.40 +/- 0.30 ng/mg by glibenclamide, gliclazide, acetohexamide, glibornuride and chlorpropamide, respectively (P less than 0.01, n = 6). Mepacrine (0.5 mM) abolished both basal and stimulated release. Thus, the enhanced PGI2 release may probably involve activation of the enzyme phospholipase A2. None of the compounds affected ADP-induced rat platelet aggregation even when the platelets were preincubated for 10 min at a concentration of 100-180 microM. The enhanced release of PGI2 may help to delay the development and progression of retinopathy, nephropathy, hypertension and thrombosis in diabetic patients prone to these diseases. Furthermore, the enhanced PGI2 release may partly underly some of the previously observed and poorly explained findings following the administration of some sulfonyl ureas into mammals.
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PMID:The influence of oral hypoglycaemic sulfonyl ureas on prostacyclin release by the rat thoracic aorta. 309 69

In arterial hypertension, hyperviscosity with hemorheological disturbances and platelet dysfunction may play a role in the prognosis and complications of the disease. We studied the effects of Nicardipine (NIC) on these blood disturbances in a group of 21 untreated patients with essential hypertension, aged 25 to 70 years (SBP/DBP = 185 +/- 28/105 +/- 17 mmHg). During one hour before and 4 hours after the IV injection of single doses of 5, 7.5 or 10 mg NIC over 5 min, blood pressure was recorded automatically (Dinamap). Hemorheological variables and platelet function were studied before and 30 min, 3 h and 24 hours after the injection. NIC lowered blood pressure and increased heart rate significantly (At 5 min, SBP = -24 mmHg; DBP = -18 mmHg; HR = +22 b/min). These effects were dose-dependent with rapid onset and short duration (less than 2 hrs). NIC decreased plasma viscosity from 1.36 +/- 0.08 to 1.30 +/- 0.07 Cst; p less than 0.01, whole blood viscosity from 22.4 +/- 2.8 to 20.7 +/- 1.5 mPas; p less than 0.05 for gamma = 0.512 s-1, and erythrocyte filterability with the Ca++ ionophore A 23187 from 16.3 +/- 3.8 to 13.5 +/- 3.1; p less than 0.01. Platelet aggregation with ADP was unchanged, but aggregation with A 23187 decreased from 46.9 +/- 21.2 to 31.3 +/- 25.6; p less than 0.05, as well as plasma levels of beta-thromboglobulin (71.2 +/- 29.8 to 55.4 +/- 24.3 ng/ml; p less than 0.02) and platelet generated malonaldehyde (7.2 +/- 1.8 to 6.7 +/- 1.4 nM/10(9) platelets; NS).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Effects of intravenous nicardipine on blood pressure, hemorheology platelet function in arterial hypertension. Dose-effect relations]. 311 84

Arterial blood pressure, serum fibrin/fibrinogen degratory products, plasma thromboxane B2, in vitro platelet aggregation, and platelet ultrastructure were studied in ten gravid ewes during fast-triggered ovine pregnancy-induced hypertension and subsequent administration of the thromboxane synthetase inhibitors CGS13080 and CGS12970. During the hypertensive period, blood pressure (p less than 0.005) and plasma thromboxane B2 levels (p less than 0.005) were significantly altered. Collagen-induced in vitro platelet aggregation lag times increased (p less than 0.01), and percent aggregation (p less than 0.05), primary (p less than 0.01), and secondary (p less than 0.005) aggregatory slopes decreased. Collagen also failed to induce aggregation in some ewes. Primary slopes of ADP-induced in vitro platelet aggregation decreased (p less than 0.01) during hypertension. Degranulation and open canalicular tubule system swelling were observed in platelets which produced abnormal or no aggregation response. However, these ultrastructural abnormalities did not necessarily correspond to hypertensive periods. Thromboxane synthetase inhibitor administration lowered blood pressure (p less than 0.005) and plasma thromboxane B2 levels (p less than 0.005). Abnormalities in collagen and ADP-induced platelet aggregation curves were also corrected, and ultrastructural abnormalities were not detected. Marked elevations in plasma thromboxane levels during ovine pregnancy-induced hypertension may have had an "exhaustive" effect on thrombocytes which was reversed by thromboxane synthetase inhibition.
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PMID:Effect of thromboxane synthetase inhibition on platelet function and morphology during ovine pregnancy-induced hypertension. 323 44

Although it has been known for many years that prolonged ingestion of ethanol may be associated with numerous side effects, among them cardiovascular alterations, e.g., hypertension, cardiac arrhythmias, strokes, and cardiomyopathy, a direct cause and effect between alcohol and injury to the cardiovascular system has only been accepted recently. However, what mechanism is responsible for these cardiovascular alterations remains to be determined. Since it is well known that chronic alcohol consumption leads to hypophosphatemia and hypomagnesemia, we designed experiments to determine if controlled depletion of either phosphorous or magnesium (Mg2+) lead, in themselves, to cardiovascular disturbances and what effects these mineral depletions exert on myocardial cellular bioenergetics. Biochemical studies were carried out on left ventricular muscle, including mitochondrial and myofibrillar preparations. With respect to phosphate depletion, myocardial creatine phosphate, ATP, and ADP levels were reduced. Phosphate depletion also reduced mitochondrial and myofibrillar creatine phosphokinase activities; significant alterations in mitochondrial oxygen consumption, acid-extractable phospholipid precursors, and mitochondrial oxidation of long chain fatty acids were noted. With respect to magnesium depletion, significant reductions in inorganic oxygen consumption was also reduced. Utilizing these data, we have proposed several schemes for possible alcoholic-induced myocardial and vascular injury.
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PMID:Hypophosphatemia and hypomagnesemia result in cardiovascular dysfunction: theoretical basis for alcohol-induced cellular injury. 329 28

Serotonin content and accumulation in platelets and its release from them, as well as changes in thrombus formation in mesenteric arterioles and venules of the small intestine have been investigated in control rats and rats with spontaneous hypertension (SHR). Serotonin accumulation in platelets was determined upon its incubation with platelets. Disodium ADP salt was used as an inductor of release. Laser-induced thrombosis was caused by microvessels exposure to impulse laser irradiation. The control animals revealed a significant difference between the initial serotonin platelet level and serotonin level upon incubation and release; in values, the values of basic thrombus-forming parameters were higher than in arterioles. In SHR there is a decrease in biogenic amine content in platelets, a depression in its accumulation and release, an increase in the time of thrombus growth, its size up to the separation of the first embolus and its length along the vascular wall. It is concluded that spontaneous hypertension is characterized by decreased functional activity of platelets and depressed resistance of arterioles and venules to thrombus formation.
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PMID:[Serotonin metabolism in thrombocytes and microvascular hemostasis in spontaneous arterial hypertension]. 334 66

Prolactin may play an important role in the pathogenesis of pregnancy-induced hypertension (PIH) and preeclampsia. In 105 normotensive nulliparous women at 28 to 32 weeks of gestation, the relationship between serum prolactin concentration (PRL) and blood pressure behaviour was examined under standardized conditions. Neither postural change from left lateral to supine recumbency nor the infusion of low doses of angiotensin-II-amide had an effect on PRL levels. Similar mean PRL levels were found in pregnant women with a low angiotensin pressor dose (ADP less than 10 ng x kg-1 x min-1) or "angiotensin sensitivity", a positive supine pressor response (delta pd greater than or equal to 20 mmHg) or an increased serum uric acid concentration (greater than 3.6 mg/dl), which are criteria for an increased risk of developing hypertensive complications. However, in the group of subjects with angiotensin sensitivity, a significant correlation was found (a) between PRL levels and the APD and (b) between PRL levels and diastolic blood pressure increase after 5 min of supine recumbency. These results may reflect diminished dopaminergic activity in the central nervous system, which could influence both blood pressure and prolactin secretion.
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PMID:Relationship between serum prolactin concentration, vascular angiotensin sensitivity and arterial blood pressure during third trimester pregnancy. 340 Oct 43


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