HUMAN CHORIONIC-GONADOTROPIN BINDING-SITES IN THE HUMAN ENDOMETRIUM

The existence of high-affinity and low-capacity specific binding sites for luteinizing hormone (LH)/human chorionic gonadotropin (hCG) has b een reported in porcine, rabbit and rat uteri. We have identified hCG binding sites in the human endometrium collected from 3 5-42-year-old ovulatory and anovulatory women. The binding characteristics of hCG to endometrial tissue preparations from ovulatory and anovulatory women showed saturability with high affinity and low capacity. Scatchard plo t analysis showed the dissociation constant of specific binding sites in the ovulatory women to be 3.5 x 10(-10) mol/l and in anovulatory wo men to be 3.1 x 10(-10) mol/l. The maximum binding capacity varied con siderably between ovulatory (3.8 5 nmol/kg protein) and anovulatory (6 .12 nmol/kg protein) endometrium. Among the divalent metal ions tested (Zn2+, Mg2+, Mn2+, Ca2+-4 mol/1), Zn2+ effected a remarkable increase in [I-125]hCG binding to the endometrium (p<0.005) whereas Mn2+ showe d a marginal increase and other metal ions did not have any effect. Da ta obtained with human endometrium indicate an influence of the functi onal state of the ovary on [I-125]hCG binding to endometrium.