EXPRESSION OF SUPEROXIDE-DISMUTASE AND XANTHINE-OXIDASE IN MYOMETRIUM, FETAL MEMBRANES AND PLACENTA DURING NORMAL HUMAN-PREGNANCY AND PARTURITION

Superoxide, an agent which attenuates the half-life of nitric oxide, i s metabolized and synthesized by superoxide dismutase (SOD) and xanthi ne oxidase, respectively. Over the last few Sears much work has focuse d on the role of nitric oxide in human parturition. The aim of this st udy was to determine whether the onset of human parturition is associa ted with a change in the expression of copper/zinc superoxide dismutas e (Cu/Zn SOD), manganese superoxide dismutase (Mn SOD) or xanthine oxi dase within the uterus. Samples of myometrium, placenta, decidua and f etal membranes were obtained from women before and after the onset of labour at term. Immunocytochemistry was used to localize Cu/Zn SOD, Mn SOD and xanthine oxidase and measure SOD enzyme activity. Cu/Zn and M n SOD-like immunoreactivity was detected in syncytiotrophoblast cells, villous stromal cells and endothelial cells of blood vessels in the p lacenta. In the myometrium Cu/Zn and Mn SOD were localized to myocytes and endothelial cells and to some vascular smooth muscle cells. In th e fetal membranes we observed staining for Cu/Zn SOD and;Mn SOD in the amnion, chorion, extravillous trophoblast and decidua. There was no d ifference in SOD enzyme activity or staining intensity for SOD between different cell types before and during labour, Xanthine oxidase immun oreactivity was identified in each of the tissues examined and again t here was no difference in immunostaining in tissues obtained from wome n delivered before or after the onset of labour. These results show th at the pregnant uterus is capable of both synthesizing and degrading s uperoxide and suggest that superoxide dismutase and xanthine oxidase m ay play a role in the maintenance of uterine quiescence during pregnan cy, but not in the initiation of parturition.