Plasma renin activity and hypertensive organ manifestations in 50-year-old males.

From a screening examination in a randomly selected third of the 50-year-old male population in Göteborg, Sweden, a 10% subsample was selected as a reference group (n=80). All untreated persons with SBP greater than 175 or DBP greater than 115 mmHg on two separate occasions made up the hypertension group (n=35). The reference group and the hypertension group were subjected to the same investigations, including BP measurement before and after rest and determination of plasma renin activity (PRA), urinary sodium and norepinephrine excretion and GFR. Plasma renin activity was approximately normally distributed in both the reference and the hypertension group. Mean values were 0.78 +/- 0.18 and 0.65 +/- 0.17 ng/ml/h respectively, the difference being almost statistically significant (0.10 greater than p greater than 0.05). There was no difference with respect to sodium excretion between the reference group and the hypertension group. In the reference group, heart rate was positively correlated to PRA and to urinary norepinephrine excretion during the day. No linear correlation between PAR and BP was found, either in the reference group, or in the hypertension group. Sodium excretion during the day was positively correlated to GFR in the hypertension group, but not in the reference group. Compared to hypertensives with normal or high sodium excretion during the day, the hypertensives with low sodium excretion during the day were characterized by a higher BP, a lower GFR and a reversed diurnal rhythm of urine excretion. Thus, low sodium excretion seemed to indicate more severe hypertension with increased renal resistance during the day. The hypertension group was also divided with regard to sodium excretion into a low, normal and high renin group. The low renin group had the lowest GFR and with rising renin group (from low via normal to high) there was a significant increase in GFR and a significant decrease in resting BP. The results indicate that low renin hypertension is not a more mild, but indeed rather a more severe form of hypertension.