Extragonadal gonadotropin receptors, their distribution and function

Area of Science:

• Reproductive Endocrinology
• Molecular Biology
• Gynecology

Background:

• Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are key pituitary gonadotropins regulating reproductive functions.
• LH and human chorionic gonadotropin (hCG) share a common receptor, with evidence of extraovarian binding sites in mammals.
• LH/hCG receptors have been identified in the human and pig uterus, specifically in endometrial and myometrial tissues.

Purpose of the Study:

• To investigate the presence and regulation of LH/hCG receptors in the uterine endometrium and myometrium.
• To explore the role of ovarian hormones, such as estradiol and progesterone, in modulating uterine LH/hCG receptor expression.
• To examine the effect of hCG on uterine contractility and electromyographic activity.

Main Methods:

• Immunocytochemical techniques to detect gonadotropin receptors in uterine tissues.
• Gene expression analysis to confirm LH/hCG receptor presence in endometrium and myometrium.
• Hormonal treatments (estradiol, progesterone) in ovariectomized animals to study receptor regulation.
• In vitro and in vivo studies to assess the impact of hCG on myometrial contractility and uterine electromyography.

Main Results:

• LH/hCG receptors are present in endometrial epithelium and stromal cells, and myometrial smooth and vascular muscle.
• Receptor levels are higher during the luteal phase, suggesting hormonal regulation.
• Estradiol and progesterone influence receptor levels, with species-specific responses observed.
• hCG treatment reduced myometrial contractility and uterine electrical activity in pigs.

Conclusions:

• Uterine LH/hCG receptors play a role in regulating myometrial contractility.
• Ovarian hormones modulate the expression of these receptors, indicating a link between the ovarian cycle and uterine function.
• The precise second messenger system for LH/hCG action in the myometrium requires further elucidation.