Uterine sensitivity for blastocyst implantation
Attempting to analyse the role of the ovarian hormones upon the onset, magnitude and loss of uterine receptivity/sensitivity, particular emphasis is given to uterine vascular changes. Information concerning the modulation by hormones of uterine micro-circulation appears essential for the understanding of the receptivity/sensitivity uterine changes. The generation, storage and release of vasoactive mediators and prostaglandins appear involved. As shown in the rat recently, the onset of uterine receptivity/sensitivity is temporarily correlated with the appearance of endometrial PGE binding sites under hormonal control. On the other hand catecholamines may also modulate the uterine vascular functions. Endometrial monoamine oxidase and catecholO-methyltransferase two enzymatic activities involved in catecholamine deactivation show hormone dependant changes parallel to the manifestation of uterine receptivity/sensitivity. The precise role of these phenomena is discussed.