The possible presence of gonadotropin receptors in nonpregnant human uterus and human fetoplacental unit was investigated by light microscope immunocytochemistry using a monoclonal antibody to rat luteal hCG/LH receptors. The receptor antibody cross-reacted with human and bovine hCG/LH receptors and appears to be directed against the receptor rather than other proteins, including HLA class I antigens. Uterus and fetoplacental unit contained receptor antibody-binding sites, which indicates the presence of hCG/LH receptors. In the endometrium these receptors were present in glandular and luminal epithelial cells as well as in stromal cells. In the myometrium the receptors were detected in circular and elongated myometrial smooth muscle and vascular smooth muscle. Comparison of immunostaining intensities, which indicates the presence of different amounts of receptors, revealed that luminal and glandular epithelial cells contained more receptors than stromal cells. These cells, in turn, contained more receptors than myometrial and vascular smooth muscle. All cells in secretory phase uterine specimens contained more receptors than corresponding cells from the proliferative phase of the cycle. Midpregnancy placenta, amniotic epithelium, chorionic cytotrophoblasts, and decidual cells contained hCG/LH receptors. At term pregnancy, while receptors in fetal membranes and decidua continue to be detected, placental tissues did not show any detectable receptors unless the tissues were pretreated with neuraminidase. This indicated that term pregnancy placenta contain hCG/LH receptors masked by sialic acid residues. Comparison of immunostaining intensities suggested that syncytiotrophoblasts contained more receptors than cytotrophoblasts at midpregnancy; mesenchymal cells or blood vessels contained no detectable receptors. There were more receptors in decidua than in fetal membranes at mid- and term pregnancy. While the amniotic epithelial receptors decreased, the receptors in chorionic cytotrophoblasts and decidual cells increased from mid- to term pregnancy. In summary, hCG/LH receptors were demonstrated in the nonpregnant human uterus, human placenta, fetal membranes, and decidua. This indicates that hCG/LH may directly regulate functions of these tissues by endocrine, autocrine, or paracrine mechanisms.

LH from anterior pituitary and hCG from placenta bind to a common receptor in gonadal and nongonadal reproductive tissues. There have been numerous examples suggesting that the brain may also contain hCG/LH receptors, yet there has been no evidence for their existence so far. We now demonstrate by reverse transcription-nested polymerase chain reaction and northern blotting that the rat brain contains hCG/LH receptor mRNA. A major receptor transcript of 2.6 kilobases and minor transcripts of 1.8 and 4.4 kilobases were found. Western immunoblotting, ligand blotting, and covalent receptor cross-linking studies have shown that rat brain also contains an 80-kilodalton receptor protein that can bind hCG and hLH, but not hFSH. Rat testis used as a positive control showed a higher abundance of multiple transcripts and an 80-kilodalton receptor protein that can bind [125I]hCG. Rat liver used as a negative control did not contain any receptor transcripts or protein. In situ hybridization, dot blotting, immunocytochemistry, and topical autoradiography have revealed that hCG/LH receptors are present in rat hippocampus; dentate gyrus; hypothalamus; cerebellum; choroid plexus; ependymal cells of third, fourth, and lateral ventricles; cortex; brainstem; bovine hypothalamus; and human area postrema. These novel findings could potentially explain numerous previous observations and suggest new possibilities concerning the regulation of brain functions by hCG and LH.

The cell composition of human and bovine corpora lutea (CL) from various reproductive states was investigated by computerized video-based interactive Bioquant image analysis system IV and by light microscope immunocytochemistry. Human and bovine CL contained more nonluteal cells than luteal cells. Human CL contained a lower number of luteal and a greater number of nonluteal cells than bovine CL. Regardless of the reproductive state, human CL contained more small luteal cells than large luteal cells. In all reproductive states except in the late luteal phase, the bovine CL also contained more small luteal cells than large luteal cells. The average sizes of all the cells in human CL were smaller than in bovine CL. Human CL contained more vascular space than bovine CL during mid and late luteal phases. The number of luteal cells increased and nonluteal cells decreased from early to mid luteal phase, and then luteal cells decreased and nonluteal cells increased in late luteal phase and in degenerating human and bovine CL. While the change of number of small and large luteal cells first occurred from early to mid luteal phase in human CL, it did not take place until the late luteal phase in bovine CL. The average size of large luteal cells in humans and of small luteal cells in cattle did not change, whereas size of the other cells changed in different reproductive states in both human and bovine CL. The cell composition of term pregnancy human CL was similar to mid or late luteal phase, whereas the cell composition of early pregnancy bovine CL was similar to mid luteal phase.(ABSTRACT TRUNCATED AT 250 WORDS)

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