Stimulation of renin secretion by various methods: optional results with hydrochlorothiazide.

Serum renin concentration (SRC) was determined in 97 hypertensive patients under basal conditions and during stimulation of renin secretion. Renin secretion was stimulated by upright posture and by either of the following means: (a) diet containing 20 mEq Na/24 hours for 3 days; (b) 300 mg i.v. diazoxide injections; (c) oral ingestion of 80 mg furosemide; (d) oral hydrochlorothiazide (HCT), 25 mg twice daily for 3 days. HCT was used in 6 patients previously treated with daizoxide and in 8 patients previously treated with furosemide. Using pairs of basal and stimulated SRC determinations, the patients could be classified as high, normal, or low renin hypertensives. HCT proved to be the most convenient stimulus as far as efficacy, reliability and the patients' tolerance were concerned, and compared well with sodium restriction.