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

Membrane phospholipase C (PLC) activation is induced by the interaction of numerous vasoactive hormones and growth factors with their receptors. Two products are liberated: inositol triphosphate (IP3) and diacyglycerol (DG). The first product liberates intracellular calcium from its stores in the sarcoplasmic reticulum and the second one activates a phosphokinase, which triggers a transmembrane Na+/H+ exchange. A cascade of metabolic events secondary to these chemical changes impinges on the expression of nuclear proto-oncogenes, which determines cell growth. Studies conducted in spontaneously hypertensive rats (SHRs) have shown that PLC is hyperreactive to various agonists and that the phenomenon is present within a variety of cells, fibroblasts, platelets, and myocytes. Therefore, it is likely that hypertension in SHRs is characterized by a diffuse and intrinsic cellular defect that cannot be considered a consequence of the hemodynamic changes of hypertension. On the one hand, enhanced intracellular calcium mobilization may play a role in arterial tone and contraction whereas, on the other hand, enhanced activation of proto-oncogenes, myc, fos, and jun, may be involved in the mechanisms of arteriosclerosis. The pattern of an evolution towards arterial cell proliferation with acquisition of a secretory phenotype with collagen production was indeed observed in cultured cells from the arterial wall.
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PMID:Hypertension and atherosclerosis. 169 95

Calcium antagonists have become widely used as antihypertensive treatment in diabetic patients, although data concerning a possible influence on glucose tolerance, insulin secretion, and platelet aggregation during long-term, placebo-controlled studies are lacking. Therefore, the effects of isradipine, a new calcium antagonist, on glucose tolerance and insulin secretion during a 75-g oral glucose tolerance test (OGTT) and on ADP- and collagen-induced maximum first-wave platelet aggregation (Tmax%) were studied in 11 type II diabetic patients with borderline hypertension. After a 2-week washout period, patients were treated with placebo or isradipine for 8 weeks in a double-blind, crossover study. Systolic blood pressure was lowered significantly after isradipine therapy compared to placebo (127 +/- 3 vs. 139 +/- 6 mm Hg; p less than 0.05). Fasting blood glucose (153 +/- 14 vs. 157 +/- 16 mg/dl; NS), glucose levels, and basal (17 +/- 4 vs. 17 +/- 2 mU/ml; NS) and stimulated insulin during the OGTT remained unchanged after either treatment. Platelet aggregation after stimulation with different concentrations of ADP and collagen showed no significant differences. These data indicate that calcium antagonists have no adverse effects on glucose tolerance, insulin secretion, and platelet aggregation in type II diabetes mellitus, and are therefore useful in the treatment of hypertension in diabetic patients.
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PMID:Platelet aggregation and metabolic control are not affected by calcium antagonist treatment in type II diabetes mellitus. 169 14

Pathological left ventricular hypertrophy in renovascular hypertension is associated with the accumulation of fibrillar collagen within the extracellular space and around intramyocardial coronary arteries. Even though the angiotensin converting enzyme inhibitor captopril was previously found to attenuate this interstitial and perivascular fibrosis, the relative importance of arterial and ventricular systolic pressures versus circulating angiotensin II (AII) and aldosterone (AL) in promoting hypertrophy and collagen accumulation in renovascular hypertension is uncertain. By drawing on the in-parallel arrangement of the right and left ventricles, with respect to their coronary circulation, and the in-series mechanical alignment of the ventricles, with a pressure-overloaded left and a normotensive right ventricle, this study sought to address this uncertainty. Three models of experimental hypertension, each having a different circulating AII and AL profile, were examined and compared with their controls: renovascular hypertension, where both AII and AL are increased; infrarenal aorta banding, where AII and AL are normal; and a chronic infusion of AL, where AII is suppressed or normal and AL is increased. In renovascular hypertension, as well as with AL, we found a significant rise in the interstitial collagen volume fraction and perivascular collagen area of the pressure-overloaded, hypertrophied left ventricle as well as the normotensive, nonhypertrophied right ventricle. This remodeling was not seen in either ventricle with infrarenal aorta banding despite comparable systemic hypertension and left ventricular hypertrophy. Thus, in experimental arterial hypertension in the rat, myocyte and nonmyocyte compartments of the myocardium are under separate controls: myocyte hypertrophy is most closely related to ventricular loading while circulating AII and AL, acting alone or in concert with other humoral factors, regulate the accumulation of collagen within the right and left ventricles.
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PMID:Remodeling of the rat right and left ventricles in experimental hypertension. 170 Sep 33

The vascular smooth muscle cell of the arterial media plays a predominant role in functional and structural alterations of the arterial wall in pathophysiological processes such as arterial hypertension, atheroma, or normal aging. The observed alterations are related to the three activities of the vascular smooth muscle cell, namely contractility, secretion of proteins from the extracellular matrix, and proliferation and migration. In arterial hypertension, vascular smooth muscle cells are functionally more contracted and structurally hypertrophic, and more collagen is secreted than under normal conditions. Similar structural changes are observed in the normal aging process. With respect to vascular smooth muscle cells, atheroma is characterized by their subintimal migration and proliferation, and by excessive excretion of collagen associated with other phenotypic modifications that are expressed in their regression to a myofibroblastic state. Regardless of the pathophysiological context, these phenotypic modifications of the vascular smooth muscle cell are always linked to an activation of the phosphoinositol pathways and to calcium accumulation. The activation of the phosphoinositol pathways seems to be a common feature of the different types of arterial hypertension. This activation can be associated with an increase in vasoactive peptides such as angiotensin II, vasopressin, or endothelin as in the secondary types of hypertension or directly related to an increase in vasoconstriction; or, as an exception, it can be spontaneously active in vivo and in vitro, as in the model of cultured vascular smooth muscle cells of the spontaneously hypertensive rat (SHR).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pathophysiological role of the vascular smooth muscle cell. 170 13

The effect of various antihypertensive medications on platelet function is of increasing interest. Conflicting effects of captopril on platelet function are reported and the impact of angiotensin converting enzyme (ACE) inhibitors not containing a sulfhydryl group such as enalapril, lisinopril, and quinapril on platelet function remains unstudied. Therefore, the aim of the present study was to examine the effect of antihypertensive treatment with quinapril, a novel ACE inhibitor not containing a sulfhydryl group, on platelet function. Ten white men (age range of 32-61 years) with untreated mild-to-moderate essential hypertension (supine diastolic blood pressure greater than 95 mm Hg) were treated with 4 weeks each of placebo and quinapril in a double-blind, randomized, crossover design. Quinapril (20 mg twice a day) significantly lowered systolic (p less than 0.01) and diastolic blood pressure (p less than 0.01) without any significant effect on heart rate or plasma catecholamines. No significant change was noted for in vitro platelet aggregation induced by epinephrine, ADP, or collagen. Plasma concentrations of the platelet release factors beta-thromboglobulin and platelet factor 4 did not change, nor did the platelet content of norepinephrine, platelet weight (mg/10 ml of blood), circulating platelet count, or platelet size. Thus, as assessed by a broad spectrum of platelet parameters, we found that antihypertensive treatment with quinapril has no significant effect on platelet function in patients with mild-to-moderate essential hypertension. These "platelet-neutral" properties of quinapril suggest that quinapril, both from a thromboembolic and a hemostatic point of view, may be a rather safe agent for treatment of hypertension.
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PMID:Platelet function during antihypertensive treatment with quinapril, a novel angiotensin converting enzyme inhibitor. 170 46

Cardiac myocyte growth is the common denominator in myocardial hypertrophy irrespective of the hypertrophic stimulus. The hypertrophic remodeling of the myocardium may or may not also include the growth of nonmyocyte cells, thereby creating the potential for heterogeneity in tissue growth. Hypertrophy, therefore, need not be a uniform process, especially if trophic factors responsible for myocyte and nonmyocyte growth are independent of one another. To examine this hypothesis further, we determined the relative importance of hemodynamic and hormonal factors in augmenting ventricular mass and cardiac fibroblast-induced collagen accumulation in several rat (Sprague-Dawley) models of arterial hypertension: renovascular hypertension (RHT), infrarenal aorta banding (IRB), and chronic aldosterone (ALDO) administration. Elevations in arterial pressure were comparable in each, whereas circulating angiotension II (Ang II) and ALDO were dissimilar: in RHT, each was increased; with IRB they were normal; and with chronic ALDO, Ang II was suppressed whereas ALDO was increased. We reasoned that because of the in-series arrangement of the ventricles, where only the left ventricle (LV) experienced an elevation in systolic pressure, the right ventricle (RV) served as a negative control regarding hemodynamic factors. Relative to the in-parallel arrangement of the ventricles, provided by the coronary circulation, the RV served as a positive control for circulating hormones.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Signals for the remodeling of the cardiac interstitium in systemic hypertension. 171 64

Hypertension leads to structural and functional adaptations which, although initially protective for the cardiovascular system, ultimately work to sustain and reinforce the hypertensive state. Although blood pressure (BP) may be effectively lowered by a variety of treatments, it is becoming clear that these structural adaptation, and the risks and consequences of hypertension, may persist long after BP has been restored to normal levels. Cardiovascular tissues appear to be highly sensitive to increased BP, responding quickly with large and proportional increases in collagen and elastin. The sensitivity of this response to increased pressure, together with the slow turnover of these connective tissue proteins, suggests a mechanism by which transient or intermittent episodes of hypertension may lead to cumulative and persistent structural changes in cardiovascular tissues. With some exceptions, studies directly investigating the reversibility of these connective tissue changes have generally confirmed that increased cardiovascular collagen and elastin persist for long periods of time after BP lowering, independent of the treatment method used to achieve that lowering. Because maintenance of elevated levels of collagen and elastin is principally caused by the slow turnover of the proteins rather than by their continued production, rapid and effective reversal of cardiovascular connective tissue changes may require the development of pharmacological agents that promote or accelerate the turnover of these proteins.
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PMID:Effects of antihypertensive drug classes on regression of connective tissue components of hypertension. 171 88

Both marked hypercholesterolemia and severe hypertension have been reported to be associated with an enhanced sensitivity of blood platelets to activating agents. To investigate a possible mutual synergistic effect of moderate hypercholesterolemia and mild hypertension on platelet reactivity, we studied in 29 patients the response to aggregating agents, ADP and collagen, and the intracellular cyclic AMP content and cytosolic Ca2+ concentration that participate, respectively, as inhibitory and stimulatory mediators in platelet responses. When compared to age- and blood pressure-matched patients with normal or slightly elevated plasma cholesterol, the patients with total platelet cholesterol higher than 6.4 mM were characterized by a decreased response to collagen and ADP (14.5 +/- 3.0 vs. 23.8 +/- 2.0 a.u. and 17.7 +/- 4.5 vs. 26.9 +/- 2.7 a.u., respectively), a tendency to a reduced cAMP content both in the basal state and after phosphodiesterase inhibition by Ro-15 2041 (2.83 +/- 0.18 vs. 3.26 +/- 0.22 mumol/10(8) cells and 4.57 +/- 0.29 vs. 5.38 +/- 0.36 mumol/10(8) cells, respectively), and no change in cytosolic Ca2+ concentration (190 +/- 11 vs. 203 +/- 13 nM). After a chronic treatment with nitrendipine (20 mg/day for 6 months), blood pressure, platelet [Ca2+]i and cAMP content decreased in the patients with normal or moderately elevated hypercholesterolemia (p less than 0.001, less than 0.001, and less than 0.05, respectively), but these effects were attenuated or absent in the patients with higher hypercholesterolemia. Plasma lipids and the platelet-aggregating response to ADP and collagen were unchanged by this long-term nitrendipine treatment in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Hypercholesterolemia modulates the effects of nitrendipine on blood pressure and platelet function in essential hypertension. 172 3

To evaluate the ex-vivo effects of labetalol, at effective vasodepressor doses, on platelet aggregation in hypertension, 30 hypertensive patients were randomized to either a labetalol or control group in a ratio of two to one. For the labetalol group, the dosage was titrated from 400 mg to 600 mg per day to achieve a fall of 10 mmHg in mean arterial pressure (MAP). No drug was used in the control group. The study lasted for 4 to 8 weeks. At the beginning and end of the study, platelet aggregation to collagen, adenosine diphosphate and epinephrine were measured according to Born's method. In contrast to the significant reduction in MAP, platelet aggregation was not altered by labetalol compared with the control group. Our data do not support the hypothesis that labetalol, at effective vasodepressor doses, inhibits platelet aggregation in mild-to-moderate hypertensive patients.
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PMID:Lack of effect of labetalol on platelet aggregation in hypertensive patients. 174 39

The myocardium contains myocyte and non-myocyte cells. A disproportionate growth of the nonmyocyte cell population can alter myocardial structure and lead to pathologic hypertrophy. Myocardial fibrosis, the result of cardiac fibroblast growth or abnormal accumulation of fibrillar collagen within the interstitial space, can adversely influence myocardial stiffness and ultimately ventricular function. We have examined the relative importance of ventricular systolic and arterial pressures and the effector hormones of the renin-angiotensin--aldosterone system in mediating this reactive fibrous tissue response in the hypertensive left and normotensive right ventricles in various experimental models of arterial hypertension. To date, our findings implicate arterial hypertension, together with an elevation in plasma aldosterone, as being contributory to the fibrosis in renovascular hypertension that creates tissue heterogeneity in either ventricle and impaired diastolic function. The endocrine properties of aldosterone in this nonclassical mineralocorticoid target tissue, the myocardium, requires further investigation.
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PMID:Myocardial fibrosis: role of ventricular systolic pressure, arterial hypertension, and circulating hormones. 178 67


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