Plasma Concentrations of Cortisol and Corticosterone in the Normal Horse

Abstract

SUMMARY The plasma concentration of cortisol and corticosterone in the normal horse was determined by competitive protein-binding analysis (radiostereoassay). The mean plasma concentration of the 2 steroids in resting horses was 5.12 μ g./ml., with standard deviation of 1.67 μ g. There were no significant differences in the mean values according to age, sex, and pregnancy. Seemingly, diurnal variations in concentrations of the steroids existed in horses; values were high in the morning and low in the evening. Plasma values were increased in horses given corticotropin ( acth ) and were decreased in those given dexamethasone.