Development of Chronic Low Plasma Volumes in Long-Term Adrenalectomized Dogs.

Abstract

Adrenalectomized dogs maintained on mineralocorticoids and salt, for long periods and used frequently for studies of insufficiency and effect of stress upon the circulation, eventually develop chronic low plasma volumes as depressed as those encountered in insufficiency, despite continuation of therapy. The low volume may persist for weeks, months, or until it is raised to normal by glucocorticoids. These animals exhibit normal activity and vigor with blood pressure, blood and plasma constituents little changed from those of normovolemic dogs. The chronic low plasma volume is assumed to be due in part to a generalized, gradual increase in vasoconstrictive activity, thereby reducing free blood flow at the vascular periphery and possibly also to loss of vasodilating reactivity of the peripheral vasculature per se owing to lack of glucocorticoids. These steroids appear active in opening up peripheral vascular channels and are necessary for reestablishing a normal volume of actively circulating fluid.