Specific Triiodothyronine Binding Sites in the Anterior Pituitary of the Rat

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Science  16 Jun 1972:
Vol. 176, Issue 4040, pp. 1252-1254
DOI: 10.1126/science.176.4040.1252


Studies with L-[125l] triiodothyronine and L-[125l] thyroxine, and with equilibrium dialysis of plasma proteins indicate that rat pituitary binds L-triiodothyronine 9.8 times as strongly as it does L-thyroxine. Injection of even small doses of nonradioactive L-triiodothyronine reduces the pituitary/ plasma ratio of radioactive L-triiodothyronine, an indication of the existence of pituitary binding sites with a limited capacity for L-triiodothyronine. Limited capacity binding sites for L-thyroxine could not be demonstrated.