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 oxid e synthase (iNOS) has been investigated in rat placenta from day 19 of gestation till delivery. iNOS has been detected at the mRNA, enzyme a ctivity and protein levels in complete placenta. Immunocytochemical de tection of iNOS was heterogeneously distributed in control placenta. I ntraperitoneal injection of pregnant rats at 21 days of gestation with lipopolysaccharide (LPS) increased the iNOS immunoreactivity in the d ecidua basalis of the placenta, and, when the mRNA levels and enzyme a ctivity were measured in total tissue, a moderate increase (approx. 16 0%) was observed. A constitutive nuclear factor kappa B activity was o bserved in placenta from both control and LPS-treated animals. These r esults indicate constitutive expression of iNOS in rat placenta.