BOVINE LUTEAL CELL PRODUCTION IN-VITRO OF PROSTAGLANDIN E(2), OXYTOCIN AND PROGESTERONE IN RESPONSE TO PREGNANCY-SPECIFIC PROTEIN-B AND PROSTAGLANDIN-F2-ALPHA

A study was conducted to determine the effects of pregnancy-specific p rotein B (PSPB) and prostaglandin F-2 alpha (PGF(2 alpha)) on bovine l uteal cell progesterone, prostaglandin E(2) (PGE(2))) and oxytocin pro duction in vitro. Corpora lutea were enucleated from multiparous cows with normal oestrous cycles during the mid-luteal (days 10-12; n = 5) or late-luteal (days 17-18; n = 5) stage. Mixed large and small cells (1.5 x 10(5) cells per well) were incubated in 500 mu l modified Ham's F-12 medium. Cells were incubated for 18 h before treatments were add ed. Cells were treated with PSPB (0, 2.5, 5.0 mu g) and PGF(2 alpha) ( 0, 100, 200 ng) in a 3 x 3 factorial arrangement. After treatments wer e added, media samples were collected at 6 and 12 h. During the 18 h p retreatment incubation, progesterone, PGE(2) and oxytocin production w as similar between the prospective treatment groups. Progesterone prod uction was greater (P < 0.001) by mid-stage than by late-stage cells. In addition, progesterone decreased (P < 0.001) as incubation time inc reased. Progesterone production was not affected by PGF(2 alpha) but P SPB increased (P < 0.02) progesterone at the 5.0 mu g dose. Late-stage luteal cells produced more (P < 0.001) PGE(2) than did mid-stage cell s; PGE(2) production decreased (P < 0.001) with increased incubation t ime. Luteal PGE(2) production increased in response to PSPB treatment (P < 0.01) and PGF(2 alpha) treatment (P < 0.001). Luteal oxytocin pro duction was greater (P < 0.01) by mid-stage compared with late-stage c ells. Oxytocin production decreased (P < 0.001) with incubation time i n mid-stage cells, but in late-stage cells oxytocin production was sim ilar over time. Neither PSPB nor PGF(2 alpha) had an effect on oxytoci n. These results indicate that PSPB does not affect luteal oxytocin, b ut does increase progesterone and PGE(2) production. In addition, PGF( 2 alpha) increases luteal PGE(2), but does not affect progesterone or oxytocin production. These data do not show an interaction between PSP B and PGF(2 alpha) in regulating bovine luteal cell endocrine function .