SULFATED GLYCOPROTEIN-1 (SGP-1) EXPRESSION IN OVINE ENDOMETRIUM DURING THE ESTROUS-CYCLE AND EARLY-PREGNANCY

This study determined effects of day of oestrous cycle and early pregn ancy on sulfated glycoprotein-1 (SGP-1) expression in ovine endometriu m. A 364-bp clone of the ovine SGP-1 mRNA was amplified from reverse t ranscribed Day-15 cyclic endometrial mRNA using the polymerase chain r eaction (PCR) and primers specific for the rat SGP-1 mRNA sequence. Nu cleotide sequence of the ovine SGP-1 cDNA shared significant identity with rat SGP-1 and human prosaposin. Ewes (n = 40) were hysterectomize d on either Day 1, 6, 11, 13 or 15 of the oestrous cycle or on Day 11, 13, 15, 17 or 25 of early pregnancy. Total cellular RNA was isolated from endometrium and subjected to Northern and slot blot hybridization analyses using an antisense cRNA probe transcribed from the ovine SGP -1 cDNA clone. A single 2.6-kb mRNA transcript was detected by Norther n hybridization analyses. Slot blot hybridization analyses indicated t hat steady-state levels of endometrial SGP-1 mRNA varied during the oe strous cycle (cubic, P < 0.02) and increased between Day 11 and Day 25 of early pregnancy (linear, P < 0.02). On Days 11, 13 and 15, endomet rial SGP-1 mRNA levels were greater in pregnant ewes than in cyclic ew es (day x pregnancy status, P < 0.01). Immunohistochemical localizatio n of SGP-1 in uterine tissues with rabbit anti-rat SGP-1 antibody reve aled intense immunoreactivity associated primarily with the endometria l epithelium. These results indicate that the ovine endometrium expres ses SGP-1, a prosaposin, and that SGP-1 expression varies during the o estrous cycle and is enhanced by the conceptus. The presence of SGP-1 in the endometrium suggests intracellular and extracellular roles for this protein in glycosphingolipid metabolism or transport in the uteri ne environment.