Functional relevance of luteinizing hormone receptor in mouse uterus

Abstract

The presence of high-affinity luteinizing hormone (LH)/human chorionic gonadotropin (hCG) receptors has been reported in porcine, rabbit, rat and human uteri. We have demonstrated binding of [125I]LH to mouse uterus, which was saturable. Scatchard plot analysis indicated Kd to be 1.37 x 10(-10) mol/l and the maximum binding capacity to be 5.24 nmol/kg protein. Attempts have been made to observe the functional relevance of gonadotropin receptor in the mouse uterus. The size and weight of the uterus remarkably decreased as a result of ovariectomy; administration of LH to ovariectomized (OVX) mice significantly increased the uterine weight in comparison to the OVX control (p < 0.01), indicating a direct effect of LH on the uterus. There was a two-fold decrease of uterine ascorbic acid content in LH-treated OVX mice as compared to the intact control. The gain in uterine weight of OVX mice by LH was due to the increase in uterine protein synthesis. The stimulatory effect of LH on OVX mice uterus appears to be mediated via steroid hormones because it significantly augmented uterine mitochondrial steroidogenesis. Since 17 beta-estradiol (E2) is known to stimulate uterine protein synthesis, the circulatory level of E2 was determined in intact, OVX and OVX + LH-treated mice. A fall in the circulatory level of E2 occurred in OVX mice as compared to the control, while treatment of LH for 7 days (three injections) significantly elevated E2 levels in OVX mice (p < 0.001). This higher level of E2 in OVX mice remains unaltered on adrenalectomy, indicating that adrenals are not the source for increased E2 levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for cross-talk between the LH receptor and LH during implantation in mice

“…Our findings confirmed and extended the results reported by Mukherjee et al (1994) that indicate that Lhcgr transcripts are present in the endometrium and are expressed throughout the oestrous cycle. Real-time RT-PCR quantification with the TaqMan method was used to quantify the level of Lhcgr expression throughout the cycle.…”

“…The contribution of uterine LHCGR signalling to the infertility of LuRKO mice was demonstrated by one group (Lin et al 2005); however, conflicting results were published by Pakarainen et al (2005), who were unable to show that orthotopic transplantation of wild-type ovaries into an LuRKO mouse resulted in impaired implantation. Nevertheless, although LHCGR has been identified previously in murine endometrium (Mukherjee et al 1994) and an embryonic LH/ hCG-like signal has been detected throughout the pregnancy in the conceptus, placenta (Wide and Wide 1979) and plasma (Gidley-Baird 1977), these findings were never confirmed or have been the subject of controversy in the field (Roberts et al 1996). In addition, to date the endometrial LHCGR ligand has never been identified in mouse blastocysts.…”

“…The LHCGR system was first described in gonadal (ovaries and testis) and non-gonadal tissues in porcine (Ziecik et al 1986), rabbit (Jensen and Odell 1988) and murine (Mukherjee et al 1994) endometrium.…”

Expression of LH receptor in nonpregnant mouse endometrium: LH induction of 3β-HSD and de novo synthesis of progesterone

“…sp. activity 210 mCi/mmol) with other cold amino acids for 6 h for monitoring of protein synthesis following the procedure described previously (Mukherjee et al 1994).…”

“…Contrary to this conventional belief, numerous studies demonstrated that the LH receptor (LHR)/HCG receptor is also present in a variety of non-gonadal tissues, particularly in the female reproductive tract (Bonnamy et al 1990, Reshef et al 1990, Lei et al 1993, Mukherjee et al 1994, Shemesh et al 1997, Ziecik et al 2005. Activation of this receptor in vivo and in vitro resulted in a wide variety of responses, which can be attributed to initiation and maintenance of pregnancy (Banaszak et al 2000, Srisuparp et al 2003, Lin et al 2005, Ziecik et al 2005.…”