In vitro examination of LH-HCG receptors in human corpora lutea of the menstrual cycle and pregnancy.

Binding of 125I-human chorionic gonadotropin (HCG) to homogenates of the human corpora lutea of the menstrual cycle and pregnancy was examined in vitro. While corpora lutea of the menstrual cycle bound 125I-HCG specifically, the corpora lutea of pregnancy from 8 weeks' gestation bound little or none of the added 125I-HCG. In the corpus luteum of the menstrual cycle the dissociation constant for HCG and the number of binding sites were analyzed by a Scatchard plot. However, from these observations along with the findings of earlier reports, it may be suggested that LH-HCG receptors remain reduced in number in the corpus luteum of pregnancy.