Stress hypertension in monkeys.

1. The influence of chronic forelimb immobilization enforcing movement in upright position on blood pressure was studied in monkeys. 2. In the course of 6 months all animals subjected to immobilization became hypertensive due to a parallel increase of systolic and diastolic pressure by about 30%. The hypertension was demonstrable both in awake and anaesthetized animals and persisted even after restitution of a normal movement regime. 3. In the chronic stage (after 15 months), the plasma renin concentration was decreased by 55%, indicating that the renin-angiotensin system activation does not participate in the maintenance of the hypertensive state. The plasma volume was diminished by 18%, while the interstitial fluid volume did not differ significantly from control values. 4. It is concluded that chronic forelimb immobilization in monkeys induces a low-renin hypertension, associated with changes in extracellular fluid compartments resembling the pattern found in the hypovolaemic type of essential hypertension.