The lh-hcg receptor of human ovary at various stages of the menstrual cycle.

Receptors specific for hCG were found in human corpora lutea and follicles. hCG and LH were found to bind at a similar receptor site. The dissociation constant for hCG ranged from 10-minus 10 to 10-minus 11 mol/1 in human corpora lutea. The number of binding sites for 125-I-hCG ranged from 10-minus 14 to 10-minus 15 moles/mg protein in human corpora lutea. The binding of 125-I-hCG to ovary was found to vary at different stages of the menstrual cycle. The binding of 125-I-hCG to human ovaries increased on days 13-15 of the cycle, then declined slightly, and increased again on days 22-23. Following day 23, there was a slow decline until day 27 when binding activity could no longer be measured. No binding could be measured by the corpus luteum after the onset of menstruation or in corpora albicans.