EFFECTS OF STAGE OF GESTATION AND UTERINE LIGATION ON OVINE PLACENTOME DEVELOPMENT AND GLYCOSAMINOGLYCANS

Effects of restricting uterine space on physical, biochemical, and his tochemical characteristics of ovine placental tissues were studied. Ew es (n = 20) were unilaterally ovariectomized, assigned to either contr ol(C; n = 10) dr unilateral (UPx; n = 10) pregnancy groups, mated (d 0 ), and hysterectomized on either d 60, 90, or 120. Placental and fetal weights and placentome wet weights (PWT) in three placental areas (AI , AII, AIII) were recorded. Placentome tissue concentrations of RNA, D NA, hyaluronic acid (HA), and protein (TP) were determined. Overall, p lacentome numbers were reduced (P < .02) 23%, but individual PWT incre ased (P < .05) 27% in UPx ewes. In UPx ewes, neither total placental n or placentome weights, fetal weights, fetal crown-rump lengths, nor PW T:fetal weight ratios were affected by treatment (Trt). In the C and U Px groups, PWT increased (P < .01) from d 60 to 90. However, compensat ory growth was confined to placental areas AII and AIII in UPx groups (treatment x area, P < .01). Treatment did not affect concentrations o f RNA, DNA, TP, or HA. However, RNA, DNA, and TP increased from d 60 t o 120 (P < .01), but HA decreased (P < .01). Histologically, placentom e cellularity increased from d 60 to 120 as area occupied by-individua l fetal chorioallantoic villi (FV) decreased. The FV stained with Alci an Blue 8X. Alcianophilia was attenuated at low pH and eliminated by p retreatment with hyaluronidase, indicating the presence of HA. Thus, i ncreased placentomal cellularity was accompanied by loss of HA from fe tal allantoic mesenchyme. Mechanisms regulating loss of HA from EV may support placental maturation and fetal growth.