Effect of Porcine Conceptus Secretory Proteins on Interestrous Interval and Uterine Secretion of Prostaglandins1

Abstract

Porcine conceptus secretory proteins (pCSP) were obtained from medium in which pig conceptuses, collected on Day 15 of pregnancy, were cultured for 30 h. Culture medium was pooled, dialyzed, and concentrated by Amicon ultrafiltration for intrauterine infusion. Serum proteins (SP) were obtained from blood collected from a Day 15 pregnant gilt and diluted for intrauterine infusion. Catheters were placed into both uterine horns and the inferior vena cava of cyclic (Day 8) gilts. Single blood samples were collected at 0800 h on Days 9, 10, and 11. On Day 11, all gilts received 1 mg estradiol-17.beta. (E2) i.m. at 0800 h. Protein infusions commenced on Day 12 and continued through Day 15, twice daily at 0800 h and 2000 h. Protein infusions per uterine horn were (1) 4.0 mg pCSP + 4.0 mg SP (pCSP, 4 gilts) and (2) 8.0 mg Sp (Sp, 4 gilts). Blood samples were collected every 15 min on Days 12 through 17 between 0805 h and 1100 h. Single blood samples were colelcted at 0800 h after Day 17 until gilts exhibited estrus. Concentrations of prostaglandin (PG) E, 13, 14-dihydro-15-keto-PGF2.alpha. (PGFM), and progesterone (P4) were measured by specific radioimmunoassays. Interestrous intervals for pCSP-treated (18.2 days) and SP-treated (18.0 days) gilts were not different (SEM = 0.8 days) and temporal changes in concentrations of P4 in plasma did nt differ between pCSP-treated (29.2, ng/ml) and SP-treated (31.2 ng/ml) gilts. Gilts treated with pCSP had higher (p < 0.01) concentrations of PGFM in plasma immediately following treatment on Days 12 through 15, and highest concentrations of PGFM were detected earlier for pCSP-treated (983.5 pg/ml, Day 13) than for SP-treated (784.2 pg/ml, Day 15) gilts. Concentrations of PGE in plasma for Days 12 through 17 were also greater (p = 0.05) for pCSP-treated (272.4 pg/ml) than for SP-treatd (154.2 pg/ml) gilts. These results indicate that pCSP do not have an antiluteolytic function in early pregnancy; rather, they stimulate uterine production of prostaglandins considered important for establishement and maintenance of pregnancy in pigs.