Renin-angiotensin system in essential hypertension.

In a random sample of normotensive and hypertensive fifty-year-old men plasma-renin-activity (P.R.A.), plasma-renin-concentration (P.R.C.), and renin substrate were measured using radioimmunoassay for angiotensin I. P.R.A. in normotensives and untreated hypertensives were normally distributed with slight skewness to the right. The mean P.R.A. for untreated hypertensives (0.65 ng. per ml. per hour) was slightly, but not significantly, lower than that of the normotensive reference group (0.78 ng. per ml. per hour). Previously untreated hypertensives who had been off treatment for four weeks had either high or low P.R.A. depending on the previous treatment. No differences in the angiotensin-generation rate were noted as judged from the P.R.A./P.R.C. ratio. No differences in the renin-substrate concentration between the groups were found. The findings suggest that renin changes in essential hypertenion are secondary to pressure changes. Thus, the renin-angiotensin system may not be of primary pathogenetic importance in the development of essential hypertension.