EFFECTS OF OESTROGEN AND PROSTAGLANDIN F2α ON LUTEINIZING HORMONE RECEPTORS IN HUMAN CORPORA LUTEA

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Abstract
The binding of 125I-labelled human LH (hLH) to the 2000 g subcellular fraction of human corpora lutea of the menstrual cycle was examined. Displacement studies demonstrated that 125I-labelled hLH was specifically bound in the 2000 g fraction of human luteal tissue. Specific binding of 125I-labelled hLH was demonstrated in all the corpora lutea examined except for two aged corpora lutea at an early proliferative phase of the cycle. The number of binding sites for hLH increased between the early to mid-luteal phase and decreased towards the late luteal phase. However, the apparent dissociation constant (Kd) in each corpus luteum did not vary throughout the menstrual cycle. In addition, the effects of treatment with diethylstilboestrol diphosphate (DES) and prostaglandin F2α (PGF2α) on the binding of 125I-labelled hLH to the 2000 g fraction of luteal tissue were investigated and the changes in hLH receptors were estimated by Scatchard analysis. The number of binding sites were 1·59 × 10−14 mol/mg protein in control tissue, 0·86 × 10 −14 mol/mg protein in DES-treated luteal tissue and 2·95 × 10−14 mol/mg protein in PGF2α-treated luteal tissue. Thus, the binding sites for hLH decreased as a result of treatment with DES and increased by treatment with PGF2α. In contrast, the apparent Kd in each luteal tissue revealed almost the same value (4·24 × 10−10 to 6·07 × 10−10 mol/l) after treatment with DES or PGF2α. The results of the present study suggest that oestrogen and prostaglandin might have an important role in modulating hLH receptor in human corpora lutea.