Thyroid hormone binds to human corpus luteum

A high affinity, low capacity 3,5,3'-triiodo-L-thyronine (T3) specific binding was detected in the nuclei preparation from human corpus luteal nuclei by using an in vitro thyroid hormone binding assay. The bound hormone was efficiently separated from free hormone by the use of 40% polyethylene glycol. Under standardized assay conditions of pH 8.6 at 37 degrees C and a 2-h incubation time, the binding in the corpus luteal nuclei was saturable with Kd 4.94 x 10(-10) M with low maximum binding capacity (1.70 p mol/mg DNA). Competitive binding studies with hormone analogues indicated that T3 binding to corpus luteal nuclei is hormone-specific. Findings indicated a direct effect of thyroid hormone on the human corpus luteum.