REGULATION OF LUTEAL REGRESSION - THE EWE AS A MODEL

This article focuses on mechanisms that regulate functional and struct ural regression of the corpus luteum (CL) with special emphasis on the role of prostaglandin F-2 alpha (PGF(2 alpha)) in mediating these eve nts in large luteal cells in the ewe. Progesterone produced by the CL is absolutely required in all mammals for implantation and early maint enance of pregnancy. Luteal regression at the end of the nonpregnant c ycle involves loss of progesterone production and tissue destruction v ia physiologic cell death, apoptosis. These are distinct events termed functional and structural regression, respectively. In many mammals, including ewes, luteal regression in initiated by prostaglandin F-2 al pha (PGF(2 alpha)) of uterine origin. However, the exact mechanisms of this regulation are not well understood. Functional regression appear s to be directly stimulated by PGF(2 alpha) via activation of its memb rane receptor. Whether structural regression is also initiated directl y by PGF(2 alpha) is not known. the ovine CL contains two morphologica lly and functionally distinct steroidogenic cell types, designated sma ll and large. Receptors for PGF(2 alpha) are exclusively located on la rge cells. Thus, the signal for regression is received in those cells. These data provide strong evidence that the intracellular determinant of regression resides within the large cell. (C) 1998 by the Society for Gynecologic Investigation.