Effects of early pregnancy and acute 17 beta-estradiol administration on porcine uterine secretion, cyclic nucleotides, and catecholamines.

This study investigated acute effects of 17 beta-estradiol (E) on ions, cyclic nucleotides, and catecholamines and their association with temporal changes in uterine secretory products in pregnant, cyclic, and nonpregnant gilts. Uterine flushings (UTF) and endometrium (ENDOM) from one uterine horn of nonpregnant and pregnant gilts (n = 9) were collected on days 10, 12, and 14 (n = 3). Protein, plasma inhibitor (P less than 0.05), Na+, and K+ (P less than 0.01) increased linearly in UTF of pregnant gilts. Ca2+ changed biphasically, with higher concentrations (P less than 0.01) in pregnant gilts on day 12. Endometrial cAMP and cGMP (P less than 0.05) increased between days 12 and 14 of pregnancy. The UTF norepinephrine (NE) concentrations increased (P less than 0.01) in cyclic gilts between days 12 and 14, while endometrial NE increased between days 10 and 12 and then decreased on day 14. The UTF of pregnant gilts had higher (P less than 0.05) concentrations of dopamine (DA), which peaked on day 12 and then decreased (P less than 0.01) by day 14. DA in UTF of nonpregnant gilts decreased between days 10 and 12 and remained low on day 14. A catecholamine metabolite, 3,4-dihydroxyphenylglycol, in ENDOM (P less than 0.05) and UTF (P less than 0.01) decreased linearly between days 10 and 14. The turnover rate of endometrial catecholamines was 2.4-fold higher (P less than 0.05) during early pregnancy compared with that in cyclic gilts. Effects of acute administration of exogenous E (0.5 mg) were also studied. The UTF and ENDOM were from day 11 nonpregnant gilts 0, 30, 60, and 360 min (n = 3) post-E or post-saline-ethanol (C) injection (n = 9). Potassium, plasma inhibitor (P less than 0.01), and cGMP (P less than 0.05) increased rapidly (30 min) after E injection. The K+ level changed biphasically, with increased concentrations again at 360 min. Plasmin inhibitor returned to levels similar to controls by 60 min, whereas cGMP remained elevated until 360 min postinjection when E, Ca2+, K+ (P less than 0.01), and Na+ (P less than 0.03) were increased. ENDOM NE (P less than 0.05) and UTF DA (P less than 0.05) were lower in E-treated gilts. Additionally, the turnover rate was significantly lower (P less than 0.05) for NE and DA in the UTF of E-treated gilts. An increase in Ca2+ in UTF preceded increases in protein secretions (except plasmin inhibitor) and may play a role in E-stimulated endometrial epithelial secretory vesicle exocytosis.(ABSTRACT TRUNCATED AT 400 WORDS)