Plasma renin activity in psychosocial hypertension of CBA mice.

Abstract

We studied plasma renin activity (PRA) in male full-color brown Agouti (CBA) mice subjected to varying degrees of psychosocial stress induced by manipulation of their housing patterns. Blood samples were obtained from unanesthetized mice by retro-orbital puncture; blood pressure (BP) was measured by tail plethysmography. At 4 months of age, PRA was lower in mice isolated since weaning (isolates) than in mice housed together in standard cages (boxed sibs). Isolation of boxed sibs for 7 days also decreased PRA. PRA did not change in isolates during a 10-month period. In contrast, PRA and BP changed markedly after 4-month-old isolates were placed in an interconnected box system [population cage (PC)] which increased social interaction and competition; values at all times were greater than those of isolated controls. PRA increased rapidly during the first 1-2 days, declined from these high values over the next 3 weeks to values similar to those of boxed sibs (but higher than control isolates), and then rose again progressively during the next 5-6 months. BP was elevated within 1 week (particularly in subordinate mice), then rose slowly throughout the experiment. During the first 2 months, PRA and BP were inversely correlated; no significant correlation existed after 2 months. Hematocrit tended to be lower in PC mice from 7 days on. Blood urea was increased in 10-month-old PC mice. Increased PRA and BP also occurred in boxed sibs placed in PC for 3-10 weeks. The pattern of PRA changes in these mice is analogous to that observed in certain forms of human essential hypertension and is further evidence that psychosocial hypertension in CBA mice may be an appropriate model for the study of essential hypertension.