Steroids arterial pressure and the baroreceptors

Abstract

1) Intravenous infusion of aldosterone raises the arterial pressure 20% in five hours. 2) Inprogesterone pretreated animals, aldosterone infusion raises the arterial pressure 45% in five hours. 3) Inprogesterone pretreated animals, arterial pressure rises 15% during a five hour saline infusion. 4) In salt fed animals, aldosterone infusion raises the arterial pressure 30% in five hours. 5) In salt deprived animals, aldosterone infusion raises the arterial pressure 10\ in five hours. 6) Interference with the ability of both carotid baroreceptors to detect elevated pressure bymeans of encapsulation results in a 38% chronic hyPertension maintained for at least 50days. 7) Infusions of noradrenaline are far less effective in raising the arterial pressure in decerebrate animals with lively baroreceptor reflexes than in decerebrate anaesthetised animals whose baroreceptor reflexes have been muted by the anaesthetic. 8) Aldosterone selectively perfused through the carotid sinus can raise arterial pressure. Aldosterone infused into animals whose carotid baroreceptors are externally perfused, and protected from exposure to the aldosterone, has no effect upon arterial pressure. Aldosterone infusion has no significant effect upon the arterial pressure of a nembutal anaesthetised animal. 9) Infusion of 0.3 mg/kg/hr of cholesterol emulsion in saline raises the arterial pressure 45% in four hours. Infusion of plasma bound cholesterol in the same amounts raises the arterial pressure 15\ in four hours. Infusion of emulsified talc in the same amount has no effect on arterial pressure. 10) Administration of a diet high in unsaturated fats to rabbits results in an elevation of arterial pressure beginning 6 days after starting the experimental diet, and reaching a peak of 40 above control after 24 days. During the course of the experiment, there was no change in the plasma cholesterol concentration.