EFFECT OF PREGNANCY-SPECIFIC PROTEIN-B ON LUTEAL CELL PROSTAGLANDIN, AND OXYTOCIN PRODUCTION ESTROUS DURING 2 STAGES OF THE BOVINE ESTROUS-CYCLE

This experiment was designed to evaluate the effects of pregnancy-spec ific protein B (PSPB) on luteal cell progesterone (P-4), PGF(2 alpha), PGE(2), and oxytocin secretion. Corpora lutea were collected during t he mid (d 10 to 12; n = 5) or late luteal (d 17 to 18; n = 5) stage of the estrous cycle. Large and small cells (1.5 x 10(5)/well) were trea ted with PSPB (0, 2.5, or 5.0 mu g) and LH (0, 50, or 100 ng) in a 3 x 3 factorial arrangement. Cells were incubated for 18 h before adding treatments; after treatments, medium was collected at 6 and 12 h. Duri ng the 18-h pretreatment period, P-4, PGF(2 alpha), PGE(2), and oxytoc in production was similar between the prospective treatment groups. Th e PSPB did not affect P-4 production. Stage of the cycle (stage) x tim e interaction (P < .001) indicated that mid-stage luteal cells produce d more P-4 than late-stage cells; regardless of stage, P-4 decreased w ith time. The time x LH interaction (P < .001) revealed that at 6 and 12 h the 50- and 100-ng doses of LH increased P-4 to greater than the 0-ng dose. Production of PGF(2 alpha), by mid-stage cells was similar among the three PSPB treatments; however, PGF(2 alpha) production by l ate-stage cells increased (P < .01) in response to the 5.0-mu g dose o f PSPB. The LH did not affect PGF(2 alpha) production. Late-stage lute al cells produced more (P < .001) PGF(2 alpha) than mid-stage cells du ring the 18-h pretreatment period and at 6, but not 12, h. Also, PGF(2 alpha) at mid and late stages was greater at 6 than at 12 h. Producti on of PGE(2) was greater (P < .001) in late-stage than in mid-stage ce lls. Also, PGE(2) production was greater (P < .001) at 6 than at 12 h. The LH did not affect PGE(2) production. The 2.5- (P < .03) and 5.0-m u g doses (P < .001) of PSPB increased PGE(2), compared with 0 mu g of PSPB. Luteal cell oxytocin production was greater (P < .001) in mid-s tage than in late-stage cells and was not affected by LH or PSPB. Thes e data indicate that PSPB does not affect bovine luteal cell P-4 or ox ytocin, but it increases PGF(2 alpha), and PGE(2) production. The LH i ncreases P-4, but LH has no effect on luteal PGF(2 alpha), PGE(2), or oxytocin production. There is no evidence of an interaction between PS PB and LH altering luteal prostaglandin, P-4, or oxytocin production.