Diurnal Rhythm in Plasma Corticosterone and Lack of Diurnal Rhythm in Plasma Compound F-like Material in the Rat.

Abstract

The concentration of corticosterone in the blood of the male rat varied from a high of 31.2 [mu]g% at 9 to 10 P. M. to a low of 7.2 [mu]g% at 2 to 3 A. M. Comparable results were obtained in the female. However, no indication of a diurnal rhythm was noted for an unknown component of adrenal origin (a compound F-like material) in the plasma of the male or female rat. These data support the concept that corticosterone is the glucocorticoid of physiological significance in the rat.