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

A role for calcium in human hypertensive disease has been suggested. However, the various, apparently contradictory, abnormalities of calcium metabolism observed in experimental and clinical hypertension do not allow for unambiguous description of the specific manner in which calcium contributes to the hypertensive process. We studied calcium metabolism in essential hypertension and used renin-sodium profiling, which reveals the biochemical heterogeneity of clinical hypertension. We observed renin-linked, heterogeneous deviations in circulating levels of the divalent cations, magnesium and ionized calcium, in addition to deviations in the calcium-regulating hormones, parathyroid hormone (PTH), calcitonin (CT), and 1,25 dihydroxyvitamin D (1,25 D). These renin-calcium metabolic deviations may both predict and contribute to the pathophysiology of salt-induced hypertension, the blood pressure effects of oral calcium supplementation, as well as the short and longer term effectiveness of calcium channel blockade. Altogether, these data suggest an intimate linkage between the hormonal control of calcium metabolism, the renin-angiotensin system and blood pressure regulation in human hypertension.
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PMID:The significance of calcium and calcium channel blockade in essential hypertension. 285 82

The renin-angiotensin-aldosterone system regulates blood pressure and volume homeostasis in addition to sodium and potassium metabolism, and may be linked to divalent cation metabolism as well as hypertensive disease. In essential hypertension, circulating serum magnesium and Ca++, and the calcium regulating hormones, parathyroid hormone, calcitonin and 1,25 dihydroxyvitamin (1,25D) are different in the various renin subgroups. Elevated blood pressure induced by such maneuvers as dietary salt loading is associated with exacerbations of these calcium metabolic deviations, and appears related to salt-induced changes in serum Ca++ or 1,25D levels. Short- or longer-term lowering of blood pressure with the calcium-channel blocker, nifedipine, or with calcium or magnesium supplementation is associated with a shift of renin system activity and calcium metabolic indexes back to average normotensive values in those subjects most susceptible to these hypotensive agents. These observations suggest that deviations in calcium metabolism in essential hypertension may be related to the pathophysiology of the hypertensive process. Further, renin system activity and calcium metabolic indexes such as serum Ca++ levels may help target specific subgroups of hypertensive populations most susceptible to various dietary or drug maneuvers, and thus may provide a basis to better understand and treat clinical hypertension.
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PMID:Renin, calcium metabolism and the pathophysiologic basis of antihypertensive therapy. 286 7

Recent information has shed a new light on the control of parathyroid hormone (PTH) secretion by calcium and 1,25-(OH)2D. These new data have permitted a better understanding of the pathogenesis and management of secondary hyperparathyroidism in end-stage renal disease. Emerging evidence has suggested a role for secondary hyperparathyroidism in the development of certain forms of hypertension and osteoporosis. Recent insights have been obtained regarding the occurrence of secondary hyperparathyroidism in obese and black subjects, in patients with multiple endocrine neoplasia type I, and in manic-depressive patients receiving lithium therapy. This review examines some of these recent gains in knowledge concerning secondary hyperparathyroidism, as well as their clinical implications.
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PMID:Update on secondary forms of hyperparathyroidism. 288 9

Current information suggests that alpha 2-adrenoceptors do not directly influence vascular resistance or Na reabsorption in the rat kidney. To reexamine the effects of alpha 2-agonists we used isolated rat kidneys perfused at 37.5 degrees C with precise measurement of renal artery pressure and flow. The recirculating perfusate contained pyruvate as the sole metabolic substrate which enabled us to use gluconeogenesis as an index of proximal tubular alpha 1-responses. Clonidine and guanfacine in 100 nM concentrations decreased phosphate excretion without altering Na, Cl, or K reabsorption or gluconeogenesis; 500 nM concentrations increased vascular resistance and decreased glomerular filtration rate and Na, Cl, and K excretion with no significant effect on gluconeogenesis. Prior thyroparathyroidectomy prevented the antiphosphaturic but not the antinatriuretic or vascular responses. Clonidine, an alpha 2-agonist with some alpha 1-activity, was a more potent vasoconstrictor than methoxamine or guanfacine. In the presence of prazosin (1 microM), norepinephrine (60 nM) stimulated phosphate reabsorption; norepinephrine alone did not stimulate phosphate reabsorption which indicates alpha 1-antagonism of this alpha 2-response to NE. These results and a literature review suggest that increased renal alpha 2-adrenoceptors could raise renal vascular resistance, reduce renin secretion, and antagonize parathyroid hormone effects on Pi, Ca, HCO3, and Na reabsorption to produce a low renin type of hypertension with increased proximal Na reabsorption and abnormal Ca and Pi excretion.
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PMID:Is there a role for renal alpha 2-adrenoceptors in the pathogenesis of hypertension? 289 22

Fourteen reports have identified an association between lower dietary calcium consumption and higher blood pressure in adults. The relationship between dietary calcium and blood pressure status of humans may be modified by a wide variety of demographic, environmental, life-style, and nutritional factors. Reduced dietary calcium intake may be a proximate cause of several of the reported biochemical abnormalities of Ca2+ metabolism including the reductions in serum ionized Ca2+ concentrations and increases in circulating parathyroid hormone levels. The paradoxical increases in intracellular free Ca2+ observed in hypertension on low dietary Ca2+ intake suggest that a primary defect in the cellular handling of Ca2+ may exist, possible mediated through defective Ca2+ adenosine triphosphatase pump activity.
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PMID:Epidemiological evidence associating dietary calcium and calcium metabolism with blood pressure. 295 Jul 55

We have found increased renal alpha 2-adrenoceptor density and a defect in prostaglandin and parathyroid stimulated adenylate cyclase in two genetic forms of rat hypertension. Changes in serum calcium and parathyroid hormone (PTH) levels suggest biologic significance to this defective adenylate cyclase response. Our hypothesis is that one or more of these defects contribute to excess renal retention of sodium and increase vascular resistance of genetically hypertensive rats and humans with essential hypertension who have similar abnormalities of calcium and PTH.
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PMID:The role of renal catecholamines in hypertension. 298 54

The relationship of arginine vasopressin (AVP) in plasma to cyclic adenosine 3' 5'-monophosphate (cAMP), sodium excretion in urine, and arterial blood pressure were determined during intravenous infusion of hypertonic sodium chloride solution (500 ml of 50 g/l) in 10 normotensive control subjects and in 11 normotensive and 10 hypertensive patients with chronic glomerulonephritis and relatively well preserved kidney function. The concentration of AVP in plasma increased 2-4 fold, osmolality in serum increased 12-16 mosmol/kg, and urinary excretion of cAMP increased 20-40% during sodium loading to the same extent in all three groups. Sodium and water excretion were higher during the sodium loading in the hypertensive patients, but not in the normotensive patients when compared to the control subjects. Neither AVP nor changes in AVP correlated significantly with changes in cAMP excretion, sodium excretion or blood pressure. In the control subjects the level of parathyroid hormone in serum was unchanged during the sodium chloride infusion. Water loading without sodium loading in eight of the control subjects caused a decrease in the excretion of cAMP. In conclusion, the increase in cAMP excretion in urine during the sodium loading might be explained by an AVP-induced stimulation of renal cAMP production. The study does not suggest that AVP plays a role in the increased sodium excretion during sodium loading or in the development of hypertension or chronic glomerulonephritis.
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PMID:Arginine vasopressin and cyclic adenosine monophosphate during acute sodium loading in chronic glomerulonephritis. 298 6

Disorders of calcium and parathyroid hormone homeostasis have been reported in subjects with essential hypertension. In many of these studies, dietary intakes of sodium and calcium were not carefully controlled. The present study was designed to compare calcium and parathyroid hormone homeostasis in normal and hypertensive subjects on controlled dietary sodium and calcium intakes and to examine the impact of dietary sodium loading on hemodynamic and metabolic responses to infused calcium. Seven subjects with essential hypertension and seven age-matched and sex-matched controls were studied while consuming a standard diet containing 600 mg of elemental calcium. Each subject was studied while consuming 10, 160, and 510 mEq of sodium per day, before, during, and after a 3-hour calcium infusion (3.75 mg/kg/hr). Before calcium infusion, hypertensive subjects had increased urinary cyclic adenosine 3',5'-monophosphate excretion independent of sodium intake (p less than 0.05). Urinary potassium excretion was greater in normotensive than in hypertensive subjects (p = 0.002). At baseline, dietary sodium intake had no effect on systolic, diastolic, or mean arterial pressure. During calcium infusion, systolic pressure increased in both groups, whereas diastolic pressure increased only when dietary sodium content was high and mean arterial pressure increased only in hypertensive subjects (p = 0.007). Together, these data provide evidence for interactions between dietary sodium intake and the cardiovascular response to calcium. They confirm that hypertensive subjects exhibit enhanced parathyroid gland function even when dietary factors are controlled, and they suggest that these subjects are more sensitive to the cardiovascular effects of short-term calcium infusion.
Hypertension 1986 Jun
PMID:Effects of calcium infusion on blood pressure in hypertensive and normotensive humans. 301 65

In a prospective study of 21 normal human kidney donors, increases in blood pressure were found in seven of 12 males and in three of nine females within the first year after uninephrectomy. Donors with blood pressure increases were characterized by greater weight and body mass indexes. In addition, urinary phosphate excretion was positively correlated (r = 0.73, p less than 0.001) and tubular reabsorption of phosphate negatively correlated (r = -0.61, p less than 0.01) with blood pressure at the follow-up periods in which increases were observed. All donors experienced an increase in parathyroid hormone levels and urinary cyclic AMP excretion. These changes were accompanied by decreases in urinary calcium and serum phosphate values. Thus, the increase in blood pressure took place in a milieu similar to that of "normocalcemic" hyperparathyroidism. The correlation of phosphate excretion and blood pressure in normal donors suggests an important role for phosphate metabolism in the genesis of hypertension associated with loss of renal mass.
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PMID:Divalent ion handling in human kidney donors with increased blood pressure after uninephrectomy. 301 74

We characterized altered adenosine 3',5'-cyclic monophosphate (cAMP) regulation in deoxycorticosterone acetate (DOCA)-Na hypertensive rats using endogenous cAMP accumulation in the intact cell system of microdissected renal tubule fragments. Increased cAMP accumulation in response to vasopressin (VP) in cortical collecting tubules (CCT) began on day 5 (67%) after exposure to DOCA-Na and increased by 320% on day 42. Increased blood pressure began after day 7 and polyuria after day 17. The increased response to VP was DOCA dependent and appears to be exaggerated by dietary NaCl. Anatomic and hormone specificity studies were done on days 21-30. These included cAMP responses to prostaglandin E2, parathyroid hormone, thyrocalcitonin, VP, and isoproterenol in the CCT. The cAMP response to VP was measured in the glomerulus, proximal convoluted tubule, thin descending limb of Henle, medullary thick ascending limb of Henle, cortical thick ascending limb of Henle, medullary collecting tubule, and CCT. The supersensitivity occurred only to VP and only in the CCT. Thus this alteration in the VP response is anatomic and hormone specific and does not appear to be an acute effect of DOCA, since it was not present on day 1 and on day 3 of DOCA exposure. DOCA-Na hypertension is VP dependent. A specific exaggerated cAMP response to this hormone in the CCT would be expected to cause increased sodium retention. Whether increased sodium retention at this site contributes to hypertension in the DOCA-Na rat is unknown.
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PMID:Enhanced cAMP response to vasopressin in the CCT of DOCA-Na hypertensive rats. 302 5


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