EN
Progesterone (P4), which is produced in the corpus luteum, determines the timing of the estrous cycle and pregnancy in many species. The physiological effect of P4 upon target cells is mediated through interaction of this hormone with two specific nuclear progesterone receptor isoforms (PR-A and PR-B), but also through non-genomic mechanisms. The non-genomic action of P4 has been found in the cells of a number of tissues, including in the female reproductive tract. However, the nature of this mechanism is still unknown. It has been determined that P4 can directly affect enzyme activity, nonspecificly change the membrane fluidity which affects receptor stability or it can bind specific membrane receptors for P4, which stimulate early intracellular signaling pathways and initiate the specific cellular response. There are at least three different proteins localized in the cell membrane, which can be a potential membrane progesterone receptor. This paper presents the latest data concerning the intracellular and membrane progesterone receptor and the genomic and non-genomic action of P4 in the female reproductive tract.