Utero-ovarian interaction in the regulation of reproductive function

The physiological regulation of fertile reproductive cycle in mammals depends on interactions between hypothalamus-pituitary, ovarian and uterine stimuli. Over the past 20 years, much has been learned about the interrelation between the affluent and effluent lymph and vascular drainage in and around both ovarian and uterine tissues. An essential feature in the regulation of the fertile cycle is the functional status of the ovary, particularly the corpus luteum. During the time of implantation and the early pregnancy, an active corpus luteum is essential. As human chorionic gonadotrophin (HCG) is important in the maintenance of the corpus luteum, we investigated if it was produced by the cyclic endometrium. Immunohistochemical and in-situ hybridization reactions were performed but neither identified the presence of HCG during the proliferative phase. Positive staining and beta-human chorionic gonadotrophin (beta-HCG) mRNA were observed during the secretory phase in the glandular cells of the endometrium. The results were confirmed by Western blotting of secretory phase endometrium extracts and assessment of the functional secretory capacity of primary endometrial cultures. Polymerase chain reaction (PCR) investigations showed a positive result in the secretory phase. We postulate that, based on the very close morphological interrelation between the uterus and the ovary, the beta-HCG of the endometrium is the primary factor for the maintenance of the corpus luteum and early pregnancy.