The inter-relationship between polyamines and the L-arginine nitric oxide pathway in the human placenta

Nitric oxide (NO) and polyamines are both products of L-arginine metabolism. In placental villous tissue NO and polyamines have been shown to be synthesized although the physiological significance is not known. We have measured polyamine (putrescine, spermidine and spermine) concentrations and nitric oxide synthase activities (NOS) in first trimester and term placentae from normal and abnormal pregnancies, but no difference was observed in polyamine concentrations between normal term and placentae from growth-retarded and pre-eclamptic pregnancies. Significantly higher levels of polyamines were found in first trimester when compared to normal term placentae and there was a significant correlation between NOS activity and the cellular polyamine levels. Cultures of a trophoblast cell line, BeWo, have been used to study the interaction of added polyamines on NOS activity. Although there was a general tendency for all the polyamines to inhibit NOS activity only putrescine was able to significantly inhibit NO production by these cells. It is thought that the L-arginine-NO-polyamine pathway may have a physiological role during pregnancy.