CORTICOSTEROID SECRETION IN KANGAROOS (MACROPUS CANGURU MAJOR AND M. (MEGALEIA) RUFUS)

Abstract

SUMMARY Adrenal venous and peripheral blood was collected from five adult and two immature kangaroos, anaesthetized with pentobarbitone. Seven C-21 Δ4, 3-oxo steroids were identified in extracts of adrenal venous blood from all animals. The major component—72–92% of detected corticosteroids—was cortisol. The remainder were 11-deoxy and 21-deoxy cortisol, corticosterone, aldosterone, 11β-OH and 17α-OH progesterone. In four out of six experiments, i.v. corticotrophin caused variable degrees of increase in corticosteroid secretion. Maximum cortisol secretion rates in all the adults and the immature male were in the range 29–70 μg./hr./100 mg. adrenal, or 28–58 μg./hr./kg. body weight and 98 μg./hr./100 mg. or 114 μg./hr./kg. in the immature female. Average aldosterone secretion rate in the adults was 0·27 μg./hr./100 mg. adrenal, or 0·18 μg./hr./kg. body weight. It was significantly higher in the immature male. However, the Na status of the animals was not known. Cortisol was the major corticosteroid in peripheral blood plasma at concentrations of 2·0–8·1 μg./100 ml. The unusual secretion of 21-deoxy cortisol suggests there may be differences in some aspects of adrenocortical biosynthesis, compared with eutherians.