Variation of Plasma and Kidney Renin Activities Among Substrains of Spontaneously Hypertensive Rats

Abstract

Plasma and kidney renin activity (PRA, KRA) were determined in the spontaneously hypertensive (SHR) rats, the stroke-resistant and -prone substrains (SHRSR, SHRSP) from 5 to 30 wk of age. Results were compared with those of 2 normotensive strains, Wistar-Kyoto (WKY) and Donryu (DON) rats. PRA in the SHRSP at 20 and 30 wk of age were significantly increased compared to other strains of rats (P < 0.01). In SHRSP at these ages, blood pressure exceeded the critical level of 220 mm Hg and cerebral lesions were observed in 41% at autopsy. There were no significant differences in PRA among other hypertensive and normotensive strains. KRA in 3 substrains of the SHR were normal or subnormal compared to WKY and DON rats. A direct role of the renin-angiotensin system in the SHR and its substrains can be excluded in the initiation and the maintenance of hypertension. The activated renin-angiotensin in SHRSP rats in the course of malignant hypertension at 20 wk of age and later, could participate in raising blood pressure above the levels of the SHR and SHRSR. There are many similarities in renin profile between the SHR and its 2 substrains and human essential hypertension in which PRA can be classified as low, normal or high.