Unresponsiveness of the Adult Toad to Thyroxine Administration. ∗

Summary

Thyroxine injected into intact toads (B. spinulosus arencum) failed to increase the water permeability and oxygen uptake of the skin and bladder, although when added in vitro it caused clear cut increases in these parameters. The hormone did, however, reduce the activity of the liver glutamic-pyruvic transaminase. This suggests that the failure of thyroxine, in vivo, to affect the metabolism and function of toad bladder or skin is not a result of end-organ unresponsiveness, but reflects some peculiarity of the metabolism or disposal of the hormone in vivo.