title: Changes in plasma thyroxine levels during and after spontaneous metamorphosis in a natural population of the green frog, Rana clamitans.
abstract: Plasma thyroxine (T4) levels were measured by radioimmunoassay in a spontaneously metamorphosing population of green frog, Rana clamitans, tadpoles. In accordance with species previously studied, a sharp rise in plasma T4 was seen at metamorphic climax, followed by a decline at final transformation. Unlike other species studied thus far, T4 levels were also moderately high in growing tadpoles (stages X-XIII). These early elevated levels may be due to daily rhythmicity in thyroid secretion coupled with the restricted hours of blood collection used in this study.
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D008675:Metamorphosis, Biological; D011893:Rana esculenta / Q000097:blood* / Q000254:growth & development; D013974:Thyroxine / Q000097:blood*
chemical_list: D013974:Thyroxine