Ovine allantoic fluid inhibition of XXXX synthesis in cotyledonary microsomes.

@entity1421 @entity3900 @entity1426 @entity3009
Inhibition of microsomal @entity3009 (PG) biosynthesis by allantoic fluid, obtained from ewes at 80-120 days of gestation, was examined. Inhibition of cotyledonary microsomal @entity1421 and PGF2 alpha biosynthesis by lyophilized allantoic fluid occurred in a dose-dependent manner. The concentration of allantoic fluid required to inhibit @entity1421 and PGF2 alpha production by 50% averaged 17.9 +/- 3.2 (S.E.M.) mg dry weight/ml (n = 5). Microsomal PG biosynthesis was markedly enhanced by the addition of @entity1426 (30 mumol/l). Synthesis of @entity1421 and PGF2 alpha was increased to 245 +/- 65% and 184 +/- 14% of control (P less than 0.05, n = 5) respectively. Treatment of cotyledonary microsomes with porcine @entity3900 ( @entity3900 ; 0.125 units/ml) also stimulated PG synthesis, @entity1421 increasing to 216 +/- 27% and PGF2 alpha to 172 +/- 14% of control (P less than 0.05, n = 5) respectively. Allantoic fluid (20 mg dry weight/ml) inhibited @entity1426 -stimulated PG synthesis ( @entity1421 by 48.6 +/- 13.8% and PGF2 alpha by 44.2 +/- 7.7%) and @entity3900 -stimulated PG synthesis ( @entity1421 by 60.6 +/- 11.6% and PGF2 alpha by 74.8 +/- 8.5%). Allantoic fluid, however, did not affect @entity3900 -stimulated release of @entity1426 from microsomes, thus negating the possibility that allantoic fluid suppresses PG synthesis by inhibiting @entity3900 activity. These data indicate that allantoic fluid inhibits PG production at the level of PG synthase enzymes. @entity3009 inhibitor(s) in allantoic fluid may play a role in maintaining uterine quiescence throughout gestation and its withdrawal, at term, may be involved in the initiation of labour.
