Expression of the calcium-independent cytokine-inducible (iNOS) isoform of nitric oxide synthase in rat placenta

The presence of the calcium-independent cytokine-inducible nitric oxide synthase (iNOS) has been investigated in rat placenta from day 19 of gestation till delivery. iNOS has been detected at the mRNA, enzyme activity and protein levels in complete placenta. Immunocytochemical detection of iNOS was heterogeneously distributed in control placenta. Intraperitoneal injection of pregnant rats at 21 days of gestation with lipopolysaccharide (LPS) increased the iNOS immunoreactivity in the decidua basalis of the placenta, and, when the mRNA levels and enzyme activity were measured in total tissue, a moderate increase (approx. 160%) was observed. A constitutive nuclear factor kappa B activity was observed in placenta from both control and LPS-treated animals. These results indicate constitutive expression of iNOS in rat placenta.