Factors affecting the development of isolation-induced hypertension in rats.

Rats were housed either individually in separate metabolic cages or in pairs in two connecting metabolic cages and systolic blood pressure was measured before and after a 5 day period over which the animals were left undisturbed. After the 5 day period isolated rats were hypertensive whereas paired rats were not. A further study compared the Na+, K+ and water balances of pairs of normotensive rats with those of isolated rats over the 5 days during which the latter became hypertensive. There was no evidence of any renal Na+ and water retention in isolated, hypertensive rats and thus it is unlikely that mineralocorticoids could have caused a plasma volume expansion and thereby contributed to the hypertension.