Evidence of a Greater Activity of LH/HCH Binding Inhibitor Present in Aqueous Extracts from Old Compared to Young Porcine Corpus Luteum

Abstract

Previously Yang, Saaman and Ward have shown the presence of an LH binding inhibitor in the 30,000 xg supernatant obtained from Parlow “pseudopregnant” and pregnant rat ovaries, which they have designated as LH receptor binding inhibitor or LHRBI. In addition, they have shown that LHRBI is a low molecular weight polypeptide of approximately 3,800 daltons (1). In 1977 Sakai, Channing and Engel demonstrated that crude extracts of porcine corpus luteum have the ability to inhibit the binding of ¹²⁵I-hCG to porcine granulosa cells from large follicles (2). They observed that the inhibitory activity was localized in luteal tissue and absent in non-luteal ovarian tissue, granulosa cells, heart and lung. This inhibitory activity increased upon freezing of the ovaries and was present in the 100,000 xg supernatant of aqueous luteal extracts.