Search for antiglucocorticoid activity in rat liver in vivo

Summary

Estradiol and testosterone both lowered endogenous liver glycogen and at 20-fold higher doses impaired triamcinolone acetonide mediated glyconeogenesis in adult adrenalectomized male rats. Neither steroid influenced liver tyrosine transaminase although tryptophan pyrrolase activity was depressed by testosterone. Progesterone increased liver tryptophan pyrrolase but did not influence other parameters. Cortexolone did not alter either of these processes whereas cortisol induced both enzymes and, at much higher dose levels, gluconeogenesis. Binding of³H-triamcinolone acetonide to its cytoplasmic receptor in vitro was left unaffected in presence of 20-fold greater concentration of either sex steroid but almost totally abolished by cold, homologous molecules. Similar results were obtained by³H-cortisol except that estradiol partially competed for³H-cortisol binding sites even at 20-fold greater concentrations of cold estradiol. Separation on DEAE-cellulose-52 and Ultrogel 44 columns revealed binding of all steroids to macromolecules of comparable physicochemical properties although the ratios of binding to the various subpopulations of the receptor were a function of the steroid in question. These results are discussed in terms of sex steroid binding to different moieties of a complex, heterogeneous, polymorphic protein rather than inhibition of binding to the active configuration acquired in presence of an inducer.