Administration of the nitric oxide synthase inhibitor NnitroLarginine methyl ester (LNAME) to pregnant rats result in fetal growth restriction and fetal hindlimb defects. However, the underlying mechanisms remain ill defined. Previous studies have demonstrated that a lack of nitric oxide production may contribute to the limb defects but not the intrauterine growth restriction(IUGR). Rather, we have previously shown that LNAME induced IUGR is associated with increased nitric oxide (NO) release from the uterus and placenta, apoptosis and nitrotyrosine formation (an index of peroxynitrite). This study was designed to assess the possible beneficial effects of the inhibitory cytokine interleukin10 (IL10) and the role of another proinflammatory cytokine tumor necrosis factor α (TNF α), in this model of fetal growth restriction. Significant IUGR and impaired placental growth were noted after the administraation of LNAME (1 mg/ml drinking water) to pregnant rats. Apoptosis, determined by TUNEL immunohistochemistry, was elevated (P < 0.05) in uterine tissue of LNAME treated animals. Apoptosis was rare in control animals. TNF α tissue content was increased in placenta and uterine tissue, although significance was achieved (p < 0.05) in the placenta. The administration of IL10 (100μg/kg/d sc) with IL10 administration prevented the restriction in placental growth induced by LNAME but, paradoxically, did not attenuate the IUGR. Uterine apoptosis was significantly reduced by IL10 treatment. Uterine and placental TNFα content were decreased with IL10 but did not reach significance. Hindlimb defects, a characteristic of this model, were reduced from 22% to 12% with IL10 (p < 0.05). Our results suggest LNAME induced IUGR is independent of placental growth and uterine apoptosis as reversal of impaired placental growth and decreased apoptosis had no effect on fetal growth. These results also demonstrate LNAME induced IUGR and hindlimb defects result from different mechanisms given the beneficial effects of IL10 on hindlimb defects but not IUGR. Further evaluation of the interplay of cytokines, growth factors and oxidants will provide insight into the regulation of fetal development and maternal tolerance of the fetal allograft.
