ESTROGEN ADMINISTRATION ON DAYS 9 AND 10 OF GESTATION DOES NOT ADVERSELY AFFECT ULTRASTRUCTURAL-CHANGES OF PORCINE UTERINE LUMINAL EPITHELIUM

Previously we demonstrated that conceptus mortality in swine is associ ated with alterations in the uterine epithelial glycocalyx after admin istration of estradiol valerate (E) on Days 9 and to of gestation. The objective of the present study was to examine ultrastructural charact eristics of the uterine epithelium following E administration. Gilts r eceived either 5.0 mg (i.m.) of estradiol valerate (n = 6) or vehicle (control; n = 6) on Days 9 and 10 of gestation. Endometrial tissue was processed for transmission electron microscopy on Days 12, 14, 16, an d 18 of pregnancy. On all days studied, surface epithelial cells linin g the uterine lumen were characterized by the presence of vesicular nu clei, prominent Golgi complexes, and abundant mitochondria. Glycogen d eposition was prominent in both control and E-treated gilts; however, glycogen accumulation was greater in E-treated gilts than in control g ilts on Day 12 of pregnancy. In control gilts, clear vesicles were mor e prominent in the apical aspect of uterine epithelial cells compared with the basal aspect on Day 12 of gestation. Dense bodies were more n umerous in the basal region compared with the apical region of the ute rine epithelium in control and E-treated gilts. Volume density (V(D)) of mitochondria was greater on Days 16 and 18 than on Day 12 of gestat ion in control and E-treated gilts. The V(D) values of rough endoplasm ic reticulum were not different between control and E-treated gilts on Days 12-18 of gestation. The V(D) value of smooth endoplasmic reticul um was greater in control gilts than in E-treated gilts only on Day 12 of gestation. These ultrastructural changes indicated an earlier incr ease in synthetic and secretory activity in E-treated gilts compared w ith control gilts and suggest that embryonic death, previously demonst rated to be associated with alterations in the uterine epithelial glyc ocalyx, did not result from any dramatic ultrastructural changes in th e uterine epithelium.