title: Binding of dexamethasone by hepatic, intestine, and tailfin cytosol in Rana catesbeiana tadpoles during spontaneous and triiodothyronine-induced metamorphosis.
abstract: The binding of the synthetic glucocorticoid dexamethasone (dex) to Rana catesbeiana tadpole liver, intestine, and tailfin cytosol during both spontaneous and triiodothyronine (T3)-induced metamorphosis has been examined. No change was observed in the dissociation constant (KD) in the liver or intestine during either spontaneous or T3-induced metamorphosis compared with liver and intestine cytosol from the frog. The binding capacity (N) in liver cytosol of premetamorphic tadpoles (14.33 x 10(-14) mol dex/mg protein) was not significantly different from that found during prometamorphosis (stage XVIII) (11.50 x 10(-14) mol dex/mg protein) and in the adult frog (19.24 x 10(-14) mol dex/mg protein). Following the onset of metamorphic climax, however, there were significant reductions in N in liver cytosol, reaching a nadir at stage XXIV (0.38 x 10(-14) mol dex/mg protein). Binding capacity in premetamorphic tadpole intestine (19.60 x 10(-14) mol dex/mg protein) was significantly reduced following premetamorphosis . Values did not return to premetamorphic values in the frog intestine (6.54 x 10(-14) mol dex/mg protein) as occurred in the frog liver, nor were values significantly reduced following the onset of metamorphic climax (10.43 x 10(-14) mol dex/mg protein) when compared with prometamorphosis (11.58 x 10(-14) mol dex/mg protein). The binding capacity in the tailfin cytosol did not deviate from premetamophic tadpole values (11.61 x 10(-14) mol dex/mg protein) through stage XXI (9.68 x 10(-14) mol dex/mg protein), the last stage in which sufficient tissue was available for analysis.
mesh_terms: D000818:Animals; D003600:Cytosol / Q000378:metabolism; D003907:Dexamethasone / Q000378:metabolism*; D005215:Fasting; D007413:Intestinal Mucosa / Q000378:metabolism*; D007814:Larva / Q000502:physiology; D008099:Liver / Q000378:metabolism*; D008675:Metamorphosis, Biological / Q000187:drug effects*; D011892:Rana catesbeiana / Q000502:physiology*; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D013623:Tail; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D011965:Receptors, Glucocorticoid; D014284:Triiodothyronine; D003907:Dexamethasone