Effect of histone-H2A (H-H2A), platelet activating factor (PAF) and pregnancy specific protein B (PSPB) on secretion of prostaglandins E and F2 alpha (PGE; PGF2 alpha) by bovine endometrium and H-H2A on basal secretion of luteinizing hormone (LH) by bovine pituitary cells in vitro.

Effects of H-H2A, PSPB or PAF on day 16 bovine endometrial secretion of PGE and PGF2 alpha and H-H2A on basal secretion of LH by bovine pituitary cells in vitro were examined in two experiments. PAF (P < or = 0.08) and H-H2a + PAF (P < or = 0.10) treatment for two hours in an in vitro perfusion system tended to increase secretion of PGF2 alpha expressed as a proportion of the prechallenge concentrations of PGF2 alpha by day 16 bovine caruncular endometrium, which occurred during the two-hour period after treatment removal. PGF2 alpha was increased (P < or = 0.02) in the two hour period after the treatment was removed in both control and H-H2A-treated endometrium. H-H2A (P < or = 0.07) and PSPB (P < or = 0.08) tended to increase PGE, while H-H2A + PSPB (P < or = 0.05) and H-H2A + PAF (P < or = 0.03) increased secretion of PGE expressed as a proportion of the prechallenge concentrations of PGE by day 16 bovine caruncular endometrium during the challenge and postchallenge treatment periods, but did not differ (P < or = 0.05) between the two-hour challenge period and the two-hour postchallenge period after removal of the treatment. In experiment two, H-H2A decreased (P < or = 0.05) basal secretion of LH by bovine pituitary cells in vitro. These data suggest that H-H2A and PSPB preferentially stimulate secretion of PGE by bovine endometrial tissue and may play a role in maternal recognition of pregnancy, while PAF increased PGF2 alpha secretion. In addition, H-H2A may play a role in regulating secretion of LH by the pituitary. Key words: Pregnancy Specific Protein B, Histone-H2A, Prostaglandin E and F2 alpha, Platelet Activating Factor, Endometrium, Cow.