Expression of 5-lipoxygenase and 5-lipoxygenase-activating protein in human fetal membranes throughout pregnancy and at term.

Lipoxygenase metabolites may be involved in human parturition. 5-lipoxygenase (5-LOX) catalyses the first steps in the synthesis of leukotrienes from arachidonic acid, and its activity is dependent on 5-LOX activating protein (FLAP). The expression of 5-LOX and FLAP were investigated in fetal membranes to determine whether there are changes with gestational age or at term with the onset of labour. No significant differences were found in the expression of 5-LOX or FLAP mRNA in the amnion at different gestational ages or at term. in the chorion-decidua, 5-LOX mRNA expression was significantly higher in the first trimester of pregnancy than in the second and third trimesters. At term, there was a significant increase in both 5-LOX mRNA and protein expression in the chorion-decidua in the time after labour, compared with the time before labour. The expression of FLAP mRNA was also significantly higher in the chorion-decidua in the first trimester of pregnancy compared with the third trimester, and at term in the time after labour compared with the time before labour. Expression of FLAP protein was not studied, as an antibody is not currently available. These results are consistent with a role for 5-LOX and FLAP in the control of parturition at term, and also suggest an involvement earlier in pregnancy.