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

In recent years abnormalities of calcium metabolism have been described in human hypertension. In this study, the relationships between indices of calcium metabolism and the renin-aldosterone system were studied in 39 subjects with untreated essential hypertension. No significant associations were found between the major determinants of calcium metabolism (plasma ionised calcium, parathyroid hormone and 1,25(OH)2-vitamin D) and the renin-aldosterone system. Serum magnesium was, however, positively correlated to plasma renin activity (PRA) (r = 0.38, P less than 0.05) while both 24 h urinary excretion of calcium and cAMP were found to be correlated to both PRA and urinary aldosterone in a positive way (r = 0.39-0.42, P less than 0.01 and r = 0.33-0.57, P less than 0.01, respectively). In this study there was no other evidence of any major influence of the renin-aldosterone status on the calcium balance in human hypertension. The urinary leak of calcium might be determined by the action of the renin-aldosterone system.
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PMID:An association between mineral metabolism and the renin-aldosterone system in human hypertension. 254 51

To determine if there are abnormalities in cellular cation regulation in pregnancy-induced hypertension, erythrocyte intracellular levels of calcium, magnesium, sodium, and potassium and circulating parathyroid hormone and "endoxin" were examined in 13 women with pregnancy-induced hypertension and 34 control subjects matched for gestational age (greater than or equal to 35 weeks). Both endoxin and parathyroid hormone levels were higher in patients with pregnancy-induced hypertension than in control subjects (endoxin, 294 +/- 34 vs. 210 +/- 19 pg/ml, p less than 0.05; parathyroid hormone, 0.65 +/- 0.05 vs. 0.60 +/- 0.03 ng/ml); the increase was significant only for endoxin. Intracellular calcium was higher in the patients with pregnancy-induced hypertension (0.033 +/- 0.010 vs. 0.015 +/- 0.001 mEq/L, p less than 0.05, in the patients with pregnancy-induced hypertension and control patients, respectively) but intracellular sodium, potassium, and magnesium levels were not different. This intracellular calcium elevation may be caused directly by the increase in parathyroid hormone or indirectly by the observed elevation in endoxin. Our data indicate that the observed effect is specific because no changes in intracellular sodium, potassium, or magnesium levels were found.
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PMID:Erythrocyte cation metabolism in preeclampsia. 237 63

To examine changes in calcium metabolism related to aging in blacks and caucasians, we measured serum mid-molecule parathyroid hormone (PTH), total and ionised calcium in 83 black and 47 caucasian healthy males aged 31-77 yrs. Age and race were without effect on total or ionised calcium. PTH levels increased significantly (P less than 0.03) with age in black but not caucasian subjects. These results demonstrate an aging-associated increase in circulating PTH in blacks and are consistent with other data from our laboratory which suggest that PTH may be involved in the development of salt-sensitive hypertension in blacks.
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PMID:Age-associated changes in parathyroid hormone in black males. 260 23

The parathyroid gland has been causally associated with some forms of hypertension, yet parathyroid hormone (PTH) has been shown to possess hypotensive properties. Recently, we described the presence of a circulating hypertensive factor in spontaneously hypertensive rat (SHR) plasma, the expression of which is associated with a novel cell type in the parathyroid gland. In order to determine whether this hypertensive factor might be produced by the parathyroid gland, the effects of parathyroidectomy and parathyroid transplantation on mean arterial pressure (MAP) and hypertensive factor activity were studied. Parathyroidectomy, but not sham operation, decreased MAP in SHR and resulted in the disappearance of the hypertensive factor from the plasma. Transplantation of SHR parathyroid glands into Sprague-Dawley (SD) rats resulted in an increase in MAP and the appearance of the factor in the plasma, whereas transplantation of SD parathyroid glands into SHR had exactly the opposite effect. SD to SD transplantation had no effect on MAP or hypertensive factor activity. Infusions of PTH gave opposite effects to hypertensive factor infusions. These results suggest that the hypertensive factor is parathyroid gland-dependent but is not PTH. On this basis, we have proposed that the factor be referred to as "Parathyroid Hypertensive Factor," or "PHF."
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PMID:Parathyroid origin of a new circulating hypertensive factor in spontaneously hypertensive rats. 261 Sep 94

The purpose of the present study was to attempt to correlate four calcium diets (0.02, 0.1, 0.5 and 2.5%) with changes in the development of hypertension in both spontaneously hypertensive and Wistar-Kyoto rats. Our findings confirm that an inverse relationship exists between dietary calcium content and the development of hypertension. The relationship does not rely upon altered serum ionized sodium, potassium, or calcium or parathyroid hormone levels. In addition, no consistent dietary calcium-dependent changes were noticed in cardiovascular reactivity. In contrast, anesthesia with pentobarbital completely abolished the relationship. These data support the hypothesis that dietary calcium influences autonomic tone through some, as yet, undefined processes.
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PMID:Dietary calcium and development of hypertension in spontaneously hypertensive rats. 261 20

The aim of this study was to assess the effect of hypercalcaemia due to primary hyperparathyroidism on the pressor and aldosterone responses to angiotensin II (Ang II) infusion. Five patients with hyperparathyroidism were studied, before and after parathyroidectomy, and were compared with five normal subjects. After 30 min of equilibration, Asp1-Val5 Ang II was infused in all subjects at stepwise increasing dose rates of 2 and 4 ng/kg per min for 30 min each. In the hyperparathyroid patients the baseline levels of plasma parathyroid hormone and calcium were significantly higher than in the controls, and returned to normal after the parathyroidectomy; plasma aldosterone and renin activity were normal both before and after the parathyroidectomy. Two hyperparathyroid patients had high blood pressure levels, which were normalized after surgery. The increase in the aldosterone response from baseline at each time point of the Ang II infusion was greater in the hyperparathyroid patients before than after the operation (P less than 0.05), and greater than in the normals (P less than 0.05). No difference in the increased response of systolic or diastolic blood pressure was observed between the hyperparathyroid patients, either before or after the parathyroidectomy, and the normal subjects. High levels of extracellular calcium or parathyroid hormone, or both, might play a primary role in the aldosterone hyper-responsiveness to Ang II in the hyperparathyroid patients. The similar pressor response to Ang II in hyperparathyroid patients and the normal subjects suggests that hypercalcaemia does not potentiate the vasoconstrictive action of Ang II.
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PMID:Aldosterone and pressor responses to angiotensin II in primary hyperparathyroidism. 263 14

Patients with essential hypertension, in particular those with low plasma renin activity (PRA), are reported to have lowered plasma-ionized calcium and elevated parathyroid hormone levels. In this study 1 microgram alphacalcidol (1 alpha-hydroxy-vitamin D3) was given in a double-blind, placebo-controlled fashion over four months to 39 subjects with mild to moderate hypertension. There was a significant rise in PRA in the treatment group when compared to placebo (P less than .05), but the mean blood pressure response was similar in the two groups. When the treatment group was divided according to pretreatment PRA it was, however, seen that subjects with low PRA displayed a reduction in diastolic blood pressure, whereas those with high PRA raised their blood pressure compared to placebo. Also subjects with low pretreatment values for plasma-ionized calcium and high levels of parathyroid hormone showed a reduction in diastolic blood pressure. This study supports the idea of a relationship between calcium metabolism and the renin-aldosterone system in essential hypertension and describes a beneficial effect of vitamin D supplementation on blood pressure in low-renin hypertension.
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PMID:Reduction of blood pressure during long-term treatment with active vitamin D (alphacalcidol) is dependent on plasma renin activity and calcium status. A double-blind, placebo-controlled study. 264 69

This review critically analyzes the available information on the relationship among calcium, parathyroid hormone, and blood pressure regulation. Both acute and chronic hypercalcemia increase blood pressure primarily via direct effects on vascular smooth muscle contractility. The evidence for indirect effects through activation of hormonal pressor systems is inconclusive. In apparent contrast with the notion that hypercalcemia can cause hypertension, more recently it has been proposed that calcium deficiency may be important in the genesis of hypertension both in humans and in spontaneously hypertensive animals. However, the evidence supporting this notion is still conflicting. Parathyroid hormone exerts complex actions on the cardiovascular system. On one hand, if injected in pharmacological doses, it is a vasodilator and antagonizes the pressor action of norepinephrine and angiotensin II; on the other hand, parathyroid hormone can potentiate the pressor effect of hypercalcemia.
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PMID:Calcium, parathyroid hormone, and blood pressure. 264 6

In a study population that comprised 34 normal black pregnant women, biochemical changes are compared between a group of women who received 1.5 gm of calcium supplementation a day and a group of women who received placebos. The blood pressure-lowering effect of calcium supplementation appears to involve a mechanism that relates parathyroid hormone and plasma renin activity. Other alterations in calcium and magnesium metabolism, as reflected by increased urinary calcium excretion and serum magnesium levels, may also contribute to this effect. Subgroups of study participants with initial (less than 26 weeks' gestation) low levels of serum calcium and plasma renin activity are the ones with the largest reductions in blood pressure. Whether these alterations can produce a reduction in the incidence of pregnancy-induced hypertension is the next question to be answered in this area.
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PMID:Biochemical changes associated with blood pressure reduction induced by calcium supplementation during pregnancy. 264 39

Recently, we described a circulating hypertensive factor, present in the plasma of spontaneously hypertensive rats (SHR). This factor seems to be produced by the parathyroid gland but is not identical to parathyroid hormone (PTH). In view of these findings, we attempted to search for histological differences in parathyroid glands between SHR and normotensive Wistar-Kyoto (WKY) rats by light and electron microscopy. Novel cells, distinct from normal chief cells, were frequently found in parathyroid glands of SHR rats, whereas they were scarcely observed in WKY rats. Our findings suggest that the novel cells are involved in the development of hypertension in SHR rats.
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PMID:A novel cell type in the parathyroid glands of spontaneously hypertensive rats. 275 10


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