Retinol-binding protein gene expression in cyclic and pregnant endometrium of pigs, sheep, and cattle.

Retinol-binding protein (RBP) is a major secretory product of conceptuses and endometrium of the large domestic animals. The present study examined the abundance of RBP mRNA in cyclic and early pregnant endometrium of pigs, sheep, and cattle and confirmed the presence of RBP mRNA in preiimplantation conceptuses of the large domestic animals. Northern blot analysis, using porcine liver RBP cDNA as the probe, detected a 1.0-1.1-kb transcript in conceptuses and endometrium collected during the preiimplantation period of pregnancy in pigs (Day 15), sheep (Day 16), and cows (Day 18). Slot-blot analysis of RBP mRNA in endometrium of pigs, sheep, and cows indicated differential RBP gene expression across days and statuses in pigs and sheep and across days alone in cows. In pigs, RBP gene expression was low to undetectable at Days 0, 5, and 10 of the estrous cycle and Day 10 of pregnancy. Levels of RBP mRNA increased (p < 0.06) from Days 10 to 12 and further (p < 0.001) to Day 15 across both statuses. At Day 18, RBP mRNA levels decreased (p < 0.01) in cyclic pigs but remained elevated in endometrium of pregnant pigs. In sheep, levels of RBP mRNA increased between Days 10 and 12 and 14 in both cyclic and pregnant ewes; however, between Days 14 and 16, RBP mRNA levels remained elevated in cyclic endometrium but decreased (p < 0.01) in endometrium of pregnant ewes. In a second experiment, RBP mRNA levels increased (p < 0.01) between Days 0-5 and Days 13-15 of the estrous cycle.(ABSTRACT TRUNCATED AT 250 WORDS)