The American journal of the medical sciences
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Comparative Study
Vasopressin: sexual dimorphism in secretion, cardiovascular actions and hypertension.
We have investigated the issue of sexual dimorphism in the secretion of vasopressin, its pressor action, and the development of deoxycorticosterone (DOC)-salt hypertension. In normal human subjects on controlled salt intake, the basal secretion of vasopressin, indicated by plasma vasopressin levels and urinary excretion of vasopressin, was higher in men than in women and in blacks than in whites. Basal vasopressin secretion also was higher in male than in female rats. ⋯ Finally, DOC-salt hypertension, which is dependent on vasopressin, developed more rapidly in male than in female rats. Although there was no sex-related difference in the extent to which plasma vasopressin levels were elevated, pressor responsiveness to vasopressin was greater and baroreflex sensitivity was attenuated to a lesser extent in hypertensive males than in hypertensive females. Thus, it seems likely that gonadal hormones play a significant role in cardiovascular regulation.
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The responses to sodium depletion and repletion were studied in subgroups of 92 normotensive and 65 borderline hypertensive individuals. The borderline hypertensives were characterized by significantly higher blood pressure, weight, cardiac output, hematocrit and decreased density of conjunctival capillaries and venules. ⋯ Sodium-sensitive individuals were characterized by significantly increased forearm vascular resistance and decreased plasma renin activity and aldosterone concentration. The resemblance of these changes to those reported in the Dahl salt-sensitive rat suggests a genetic basis for the response to sodium.
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Hypertension can precipitate renal failure in blacks. The key hypertensive lesion in the renal vasculature is severe intimal thickening in interlobular arteries without fibrinoid necrosis. ⋯ In view of this, it is likely that the low K diet characteristically consumed by blacks exaggerates their hypertensive intimal thickening. A high K diet could possibly preserve these arteries and avert much renal failure.
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The authors report the longest-lived patient with homozygous familial hypercholesterolemia, the seventh case of a defect in internalization of low-density lipoprotein (LDL). The patient is a 57-year-old man, whose plasma total cholesterol (TC) and LDL-cholesterol (LDL-C) concentrations were 465-660 mg/100 ml and 461 mg/100 ml, respectively, while his plasma high-density lipoprotein-cholesterol (HDL-C) was 13.6-16.9 mg/100 ml. ⋯ His coronary angiogram revealed diffuse coronary artery narrowing. Receptor studies revealed that his fibroblasts bound as much LDL as normal cells, but could not internalize or degrade LDL.
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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. ⋯ 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.