Human chorionic gonadotropin binding sites in the human endometrium

Abstract

The existence of high-affinity and low-capacity specific binding sites for luteinizing hormone (LH)/human chorionic gonadotropin (hCG) has been reported in porcine, rabbit and rat uteri. We have identified hCG binding sites in the human endometrium collected from 35–42-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 plot analysis showed the dissociation constant of specific binding sites in the ovulatory women to be 3.5 × 10−10 mol/l and in anovulatory women to be 3.1 × 10−10 mol/l. The maximum binding capacity varied considerably between ovulatory (3.85 nmol/kg protein) and anovulatory (6.12 nmol/kg protein) endometrium. Among the divalent metal ions tested (Zn2+, Mg2+, Mn2+, Ca2+—4 mol/l), Zn2+ effected a remarkable increase in [125I]hCG binding to the endometrium (p<0.005) whereas Mn2+ showed a marginal increase and other metal ions did not have any effect. Data obtained with human endometrium indicate an influence of the functional state of the ovary on [125I]hCG binding to endometrium.

Stimulation of pregnenolone metabolism and aromatase activity by luteinizing hormone in mouse uterus

“…From the present study, as well as from some earlier reports (8,9,11), it is clear that the mechanism by which LH exerts its stimulatory effect in the mouse uterus involves its initial binding with an LH-specific receptor in the uterine cell membrane and the activation of adenylate cyclase activity to produce cAMP which, in turn, stimulates the synthesis of P 4 . The high rate of conversion of cholesterol to P 5 in LHstimulated OVX mouse uterine tissue, reported previously by us (9), not only indicates the earlier action of LH on uterine mitochondrial steroidogenesis but also justifies the availability of P 5 within the cells of this organ for subsequent conversion to C 19 steroids.…”

“…Of these, the studies on the uteri of both primates and non-primates have been the most extensive. The presence of high-affinity and low-capacity binding sites for LH and hCG has been reported for the uterine tissue of pigs, rats, mice and rabbits (7±10), as well as for human endometrium and myometrium (1,2,11). The concentrations of uterine receptors fluctuate with the stages of reproduction.…”

Is human chorionic gonadotropin directly involved in the regulation of human implantation?

“…Several groups have demonstrated the presence of hCG/LH-binding sites and receptor-like immunoreactivity in the porcine, rabbit, rat, mouse, bovine and human endometrium (Bernardini et al 1995;Bhattacharya et al 1993;Bonnamy et al 1993;Fazleabas et al 1999;Freidman et al 1995;Jensen and Odell 1988;Lin et al 1994;Reshef et al 1990;Ziecik et al 1986) . Receptor expression seems to be cycle dependent with secretory endometria expressing higher levels as compared to proliferative or postmenopausal samples.…”

Oestrogen-dependent expression of LH/hCG receptors in pig Fallopian tube and their role in relaxation of the oviduct

“…However, the existence of specific, high-affinity, low capacity binding sites for LH/hCG has been reported in the pig (Ziecik et al, 1986), rabbit (Jensen and Odell, 1988;Sawitzke and Odell, 1991), rat (Bonnamy et al, 1990; Sawitzke and Odell, 1991), bovine (Friedman et al, 1995) and human uterus (Reshef et al, 1990;Bhattacharya et al, 1993). Moreover, LH/hCG receptors are present in the myometrium (Reshef et al, 1990;Környei et al, 1993), endometrium (Reshef et al, 1990;Bhattacharya et al, 1993) as well as in the uterine broad ligament .…”

“…However, the existence of specific, high-affinity, low capacity binding sites for LH/hCG has been reported in the pig (Ziecik et al, 1986), rabbit (Jensen and Odell, 1988;Sawitzke and Odell, 1991), rat (Bonnamy et al, 1990; Sawitzke and Odell, 1991), bovine (Friedman et al, 1995) and human uterus (Reshef et al, 1990;Bhattacharya et al, 1993). Moreover, LH/hCG receptors are present in the myometrium (Reshef et al, 1990;Környei et al, 1993), endometrium (Reshef et al, 1990;Bhattacharya et al, 1993) as well as in the uterine broad ligament . The myometrial LH/hCG receptors play a role in uterine hyperplasia and hypertrophy (Környei et al, 1993), as well as in uterine motility (Flowers et al, 1991;Ziecik et al, 1993;Eta et al, 1994), and hCG has a relaxing effect on pig (Flowers et al, 1991;Ziecik et al, 1993) and human (Eta et al, 1994) myometrium.…”