REORIENTATION OF PROSTAGLANDIN-F SECRETION BY CALCIUM IONOPHORE, ESTRADIOL, AND PROLACTIN IN PERIFUSED PORCINE ENDOMETRIUM

Establishment of pregnancy in pigs requires a shift in endometrial prostaglandin (PG) F secretion from an endocrine (toward the myometrium and uterine vasculature) to an exocrine (toward the uterine lumen) orientation. Three experiments utilized bilateral endometrial perifusion devices for separate perifusion of myometrial and luminal surfaces to determine whether promoting calcium cycling across the luminal epithelial surface, which may be induced by interactive effects of estradiol and PRL, is involved in the reorientation of PGF secretion during establishment of pregnancy in pigs. In Exp 1, endometrium from cyclic gilts (n = 7) on day 14 after estrus was perifused with either saline (control) or calcium ionophore A23187 added to luminal surface perifusion buffer. In Exp 2, cyclic gilts (n = 7) at day 11 after estrus received an im injection of estradiol valerate (EV) after unilateral hysterectomy and the remaining EV-stimulated uterine horn removed at 6 h (n = 3) or 12 h (n = 4) after EV. Both surfaces of these endometrial samples were perifused with buffer containing either 250 ng/ml BSA or porcine PRL. In Exp 3, endometrium from cyclic (n = 3), pregnant (n = 4), and EV-induced pseudopregnant (n = 4) gilts was collected on day 14 after estrus and perifused with BSA or PRL to both surfaces. Orientation of PGF secretion was initially endocrine in Exps 1 and 2 (P < 0.01). In Exp 1, calcium ionophore shifted the orientation of PG secretion from endocrine to exocrine (P < 0.01). In Exp 2, neither EV in vivo nor PRL in vitro alone altered the orientation of PGF secretion. However, EV and PRL interacted to reorient secretion of PGF from endocrine to exocrine at 6 h (P < 0.01) and 12 h (P < 0.01) after EV. In Exp 3, the orientation of PGF secretion was endocrine in cyclic gilts and exocrine in pregnant and pseudopregnant gilts (status x side; P < 0.05). PRL did not alter the orientation of PGF secretion regardless of reproductive status. These results suggest that the reorientation of endometrial PG secretion in pigs during the establishment of pregnancy involves interactive effects of estrogens and PRL, possibly through increased calcium cycling across the uterine epithelium. (Endocrinology 127: 637- 642, 1990). © 1990 by The Endocrine Society.