HIGH CORTICOSTEROID LEVELS IN PLASMA OF ADULT AND FOETAL WEDDELL SEALS (LEPTONYCHOTES WEDDELLI)

Abstract

Pregnant and non-pregnant Weddell seals and fetuses had very high plasma concentrations of corticosteroids (1-7 .mu.mol/l) that were unaffected by stress. Cortisol comprosed most of the corticosteroid in the adult but only 50% of that in the fetus. The affinity constant (4.30-5.53 .times. 107 l/mol) and specificity of CBG [corticosteroid binding globulin] and the MCR [metabolic clearance rate] (4.5 l/ day per kg lean body mass) in adult seals were similar to those of man. The binding capacity of CBG (1.48-1.86 .mu.mol/l) which is approximately 3 times that of man contributed to the high plasma corticosteroid concentrations but the main factor was the cortisol turnover rate of 3670 .mu.mol/day (1.3 g/ day) which is the highest value reported in any species.