A Continuous System Model of Adrenocortical Function

Control of arterial pressure and renal function during glucocorticoid excess in dogs.

“…Studies in which hypertension has been produced by glucocorticoid ad- ministration have usually been conducted in rats, 67 and the doses of steroids used have been as high as 40 mg/kg per day, which is 400-800 times greater than the normal secretion rate of carbohydrate-active steroids. 8 The mechanisms whereby massive doses of glucocorticoids cause hypertension in the rat are not entirely clear, but some investigators have suggested that the elevated blood pressure is caused either by redistribution of body fluid volumes 8 or by increased activity of the renin-angiotensin system due to increased renin substrate production.' On the basis of short-term studies, glucocorticoids have also been suggested to potentiate the vasoconstrictor action of angiotensin II (All).…”

Transitioning from Basic toward Systems Pharmacodynamic Models: Lessons from Corticosteroids

“…The major goal of a systems approach in biology was to develop theories (mathematical models) to serve as "gestalts" for interpreting experimental observations and pave the way to establish biology as an "exact" science. These ideals are consonant with the works of pioneering systems physiologists such as Yates et al (1968), who stated that "a system of coupled, connected and interacting biological components has properties beyond those that can be discovered by analysis of the components in isolation" and, relatedly, that "the objective of systems biology is to determine the dynamic attributes of a biosystem of interest, and to rationalize these attributes in terms of particular properties of the components, signals, and connections involved". Many modern conceptions of physiologic control are deeply rooted in systems theories ranging from feedback and homeostasis (Cannon, 1929) to allometry and ontogenic growth (Adolph, 1949;von Bertalanffy, 1950).…”