THE ROLE OF OXYTOCIN IN CELL-TO-CELL COMMUNICATION IN THE CORPUS-LUTEUM

Corpus luteum insufficiency (CLI), which leads to the development of o ut-of-phase endometria, results from the inadequate production of prog esterone from the corpus luteum, We have hypothesized that the cellula r components of the corpus luteum, which include the steroid-producing cells, the ''large cells'' and the ''small cells,'' as well as nonste roid producing cells, the endothelial cells, fibrocytes, and macrophag es, communicate with each other in the adequate production of progeste rone. Because only one cell type (the small cell in the human and babo on corpus luteum) responds to pituitary luteinizing hormone (LH), cros s talk between cells must occur. Established evidence indicates that p ituitary LH orchestrates the functioning of these cells. It is also cl ear, however, that factors produced by the cellular components moderat e the activity of the corpus luteum, Oxytocin is likely to be such a f actor, Oxytocin and its receptor both are synthesized by human and bab oon (Pa (Papio anubis) corpora lutea, Studies of the direct effect of oxytocin on progesterone synthesis in several in vitro models have pro duced conflicting data, The reason for this is likely to be that ''con tact dependent'' communication between cells is necessary for the prod uction and secretion of progesterone. Evidence is provided for the pre sence of gap junctions, which allow electrical and metabolic coupling between cells. The role of oxytocin in the regulation of the gap junct ion protein connexin-43 expression, and progesterone production by the corpus luteum cells, is discussed in the context of CLI.