title: Corticoids augment nuclear binding capacity for triiodothyronine in bullfrog tadpole tail fins.
abstract: The effect of aldosterone and corticosterone on T3 binding to the nuclear fraction of the tail fin of bullfrog tadpoles was investigated in vitro. Both corticoids (10(-7) - 10(-5) M) added to the incubation medium increased T3 binding in a dose-dependent manner. The aldosterone-induced increase in T3-binding was blocked by cycloheximide, an inhibitor of protein synthesis, and actinomycin D, an inhibitor of RNA synthesis. Scatchard analysis revealed that 10(-6) M aldosterone and corticosterone increased the maximum binding capacity for T3 by 60 and 41%, respectively, and that the corticoids did not alter the value of the dissociation constant. The significance of the finding is discussed in relation to metamorphosis.
mesh_terms: D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D001665:Binding Sites; D003345:Corticosterone / Q000494:pharmacology*; D004247:DNA / Q000378:metabolism; D066298:In Vitro Techniques; D007814:Larva / Q000187:drug effects; D008675:Metamorphosis, Biological / Q000187:drug effects*; D012313:RNA / Q000378:metabolism; D011892:Rana catesbeiana; D013623:Tail; D014284:Triiodothyronine / Q000378:metabolism*
chemical_list: D014284:Triiodothyronine; D000450:Aldosterone; D012313:RNA; D004247:DNA; D003345:Corticosterone