Nongonadal LH/hCG receptors in pig: Functional importance and parallels tohuman

Luteinizing hormone (LH) and human chorionic gonadotropin (hCG) share a com mon receptor in gonadal cells; however, the presence of these receptors has also been detected in several nongonadal but reproduction-associated tissu es of pig, human, and other species. There are no data about the ontogeny o f the human LH/hCG receptor. The expression of the porcine LH receptor gene in the uterus starts about 10 days after the appearance of this gene in go nads. LH/hCG receptors were found in uterus (myometrium, endometrium), ovid uct, cervix, fetal membranes, and umbilical cord in humans and pigs. The ma in role of LH/hCG receptors in myometrium is stimulation of growth and hype rplasia and relaxation of uterine motility. hCG also increases blood flow i n the uterine artery. LH and hCG can increase production of prostaglandins in endometrium, oviduct, and blood vessels. It is suggested that the preovu latory surge of LH plays an important role in controlling oviductal contrac tions. Human and pig mammary glands also possess LH/hCG receptors through w hich gonadotropins can affect the metabolism of steroid hormones in this ti ssue and may play an inhibitory role in mammary carcinogenesis and in the g rowth of breast tumors.