[Studies on luteinizing hormone receptors of human corpora lutea during menstrual cycle and pregnancy]

Abstract

With the purpose of explicating the lifespan of human corpora lutea, using human corpora lutea of the menstrual cycle and pregnancy, binding of 125I-LH to the 20,000g cell membrane fraction was examined. 1) Specific bindings of 125I-LH, 125I-HCG were demonstrated in the 20,000g cell membrane fraction. Although LH and HCG were parallel in inhibiting 125I-LH binding, HCG was found to be more effective. FSH did not inhibit binding. 2) Binding of 125I-LH was dependent on time, temperature, 125I-LH concentration, amount of the cell membrane fraction protein and pH. The highest binding was seen at pH 6.0 while incubating for 60 min at 37 degrees C. 3) The number of LH receptors in human corpora lutea of the menstrual cycle increased towards midluteal phase, especially on 5th day from ovulation, and decreased towards late luteal phase. LH receptor was not found in corpus albicans. The apparent dissociation constant of each corpus luteum did not change throughout the menstrual cycle. 4) Corpora lutea of pregnancy contained a few or no receptors which bound 125I-LH specifically. These data suggest that LH receptor is an important factor regulating the lifespan of corpus luteum and exogenous HCG has effect on luteal insufficiency, but the effect of HCG on threatened abortion is uncertain.