Interference of metyrapone with the actions of cortisol in Xenopus laevis Daudin and the laboratory rat

Abstract

Injection of cortisol into X. laevis produced a decrease in body weight and increases in liver weight, hepatic glycogen content and transaminase activity. There was a large increase in the rate of excretion of urea while ammonia excretion was only slightly increased. In rats, cortisol injection was followed by decreased body and thymus weight and increases in liver weight, glycogen concentration and transaminase activity. In X. laevis, injection of metyrapone (SU4885) was followed by a slight decrease in body weight, a 50% decrease in the rate of urea excretion but no change in liver weight, glycogen concentration or transaminase activity or in the rate of excretion of ammonia. In the rat there was a slight decrease in thymus weight but no change in the other parameters of cortisol activity. Injection of metyrapone for several days followed by injection of metyrapone plus cortisol gave exactly the same results, in X. laevis, as injection of metyrapone alone. Following similar treatment in the rat, there was a slight decrease in body weight, no change in liver weight or glycogen concentration, a decrease in thymus weight and an increase in transaminase activity; in no case, however was the change as large as that which followed cortisol injection. It is concluded that metyrapone interferes in some way with the action of circulating cortisol as well as inhibiting its biosynthesis.