Nychthemeral Variations in Plasma Free Corticosteroid Levels of the Rat.

Abstract
Nychthemeral variations in levels of plasma free corticosteroids in the rat have been observed, with highest concentrations of steroid between 4 p.m. and midnight. The magnitude of these cyclic variations is such that they will have to be considered in measurement of “resting levels” of plasma corticosteroids in this species.