Influence of thiazide on salt hypertension.

This study was undertaken to evaluate the effect of chronic diuretic therapy with chlorothiazide on the course of salt hypertension in hypertension-resistant (R) and hypertension-sensitive (S) strains of rats. Investigation of the effects of chlorothiazide on blood pressure, 24-hour urinary 24Na and aldosterone excretion, and plasma renin activity (PRA) produced the following observations: (1) Chlorothiazide failed to prevent the development of salt hypertension in S rats. (2) After 12 weeks, S rats on high salt puls chlorothiazide exhibited a rapid fall in blood pressure to levels indistinguishable from those of S rats on low salt. (3) Chlorothiazide significantly increased urinary 24Na excretion only in S rats on high salt (P less than 0.01). (4) Chlorothiazide significantly increased PRA and urinary aldosterone excretion in both strains on low or high salt diets (P less than 0.001). (5) Morbidity and mortality of salt hypertension were alleviated by chlorothiazide treatment. The unique aspect of this study is the finding that chlorothiazide did not abolish the hypertensiogenic action of salt in S rats.