CONCEPTUS, PROGESTERONE, AND BREED EFFECTS ON UTERINE PROTEIN SECRETION IN SWINE

This experiment consisted of the following treatment-breed groups: 1) White crossbred gilts, 2) White crossbred gilts treated with progester one (200 mg/d in corn oil given on d 2 and 3 after estrus), and 3) Chi nese Meishan gilts. Pregnant and nonpregnant gilts (n = 3 to 6) from e ach treatment-breed combination were assigned to be slaughtered on d 1 0, 11, 12, 13, and 15. At slaughter each uterine horn was flushed with 20 mt of minimal essential medium. Uterine flushings were assayed for total protein, acid phosphatase, uteroferrin, retinol-binding protein , and oxytocin. Uterine flush total protein was increased by progester one treatment, was unaffected by pregnancy status, and was less in Mei shans. Similar patterns were found for retinol binding protein and ute roferrin, except that uteroferrin was greater in pregnant than in nonp regnant gilts. Oxytocin was greater in pregnant than in nonpregnant gi lts, was not influenced by progesterone treatment, and was similar in Meishan and in White crossbred gilts. These results indicate that the conceptus does not influence secretion of either total protein or reti nol binding protein during pregnancy and that the onset of secretion o f these uterine proteins may be controlled by progesterone. The presen ce of the conceptus is associated with increased uteroferrin and oxyto cin production. The decreased secretion of uterine proteins in Meishan gilts may partially explain the slower embryonic development that has been reported for this breed.