Characterization of LH/hCG receptor binding inhibitor in corpora lutea of human and sheep ovaries.

Abstract

Yang, Samaan, and Ward (1976) were the first to report the presence of a luteinizing hormone receptor binding inhibitor (LHRBI) in heavily luteinized rat ovaries. It was partially purified and found to be a peptide of approximately 3800 daltons. Sakai et al. (1977) found a similar inhibitor in corpora lutea of porcine ovaries, but not in other ovarian tissues. These crude porcine luteal extracts inhibited basal and LH-stimulated progesterone secretion by cultured granulosa cells of large porcine follicles (Kumari et al., 1979). In another in vitro system using ovarian slices, Yang and his colleagues (1979) demonstrated the inhibition of LH-stimulated progesterone synthesis in presence of luteinized rat ovarian extracts. These observations, as well as the finding of increased extractable LHRBI activity in old porcine corpora lutea compared to those of early luteal phase (Kumari et al., 1979) pointed to the importance of LHRBI in regulating the follicular responsiveness to LH and regression of corpus luteum under normal physiological conditions.