Prostaglandin F2 alpha, progesterone and oxytocin production by cultured bovine luteal cells treated with prostaglandin E2 and pregnancy-specific protein B.

The objectives of this experiment were to study the effects of pregnancy-specific protein B (PSPB) and prostaglandin E2 (PGE2) on bovine luteal cell progesterone (P4), prostaglandin F2 alpha (PGF2 alpha) and oxytocin production. Corpora lutea were collected during the mid- (days 10-12; n = 5) or late-luteal (days 17-18; n = 5) stages of the estrous cycle. Luteal cells were dispersed and accessory cells removed. Luteal cells (1.5 x 10(5)) were incubated in a 3 x 3 factorial arrangement and treated with PSPB (0, 2.5, or 5.0 micrograms) and PGE2 (0, 100, or 200 ng) in 500 microL of Ham's F-12 medium. All cells were incubated for 18 h before adding treatments. Samples were then collected at 6 h and 12 h. During the 18 h pretreatment period, P4, PGF2 alpha, and oxytocin production was similar between the prospective treatment groups. The PSPB failed to increase P4 production. The PGE2 x time interaction showed that P4 increased in response to PGE2 treatment at 6 h (P < 0.001) and 12 h (P < 0.03). Also, the stage x time interaction indicated that mid-stage cells produced more (P < .001) P4 than late-stage cells during the pretreatment period at 6 h and 12 h. The PSPB did not alter PGF2 alpha production by mid-stage cells, but increased (P < .05) PGF2 alpha by late-stage cells. Also, PGE2 stimulated (P < 0.001) PGF2 alpha secretion by both mid- and late-stage cells; luteal cells treated with 200 ng of PGE2 produced more (P < 0.001) PGF2 alpha than 100 ng of PGE2. Oxytocin secretion was not changed by treatment with PGE2 or PSPB. Oxytocin production was greater (P < 0.001) by mid-stage than late-stage cells during the pretreatment period at 6 h and 12 h. Oxytocin production was similar between the 6 h and 12 h culture times within stage of the cycle. These data indicate that PSPB does not change bovine luteal cell P4 or oxytocin production, but elevates PGF2 alpha in late-stage cells. The PGE2 increases both P4 and PGF2 alpha, but does not alter oxytocin production. Lastly, PSPB and PGE2 do not interact to promote P4 PGF2 alpha, or oxytocin production by cultured bovine luteal cells.