Nitric oxide acts through different signaling pathways in maturation of cumulus cell-enclosed mouse oocytes

Nitric oxide [NO] have a dual action in mouse oocyte meiotic maturation which depends on its concentration, but the mechanisms by which it influences oocyte maturation has not been exactly clarified. In this study different signaling mechanisms which exist for in vitro maturation of meiosis was examined in cumulus cell-enclosed oocytes [CEOs] after injection of pregnant mare's serum gonadotropin [PMSG] to immature female mice. The CEOs were cultured in spontaneous maturation and hypoxanthine [HX] arrested model. Sodium nitroprusside [SNP, an NO donor, 10mM] delayed germinal vesicle breakdown [GVBD] significantly during the first 5 hrs of incubation and inhibited the formation of first polar body [PB1] at the end of 24 hrs of incubation. SNP [10-5M] stimulated the meiotic maturation of oocytes significantly by overcoming the inhibition of HX. Sildenafil [a cGMP stimulator, 100 nM], had a significant inhibitory effects on both spontaneous meiotic maturation and HX-arrested meiotic maturation. Forskolin [an adenylate cyclase stimulator, 6 micro M] and SNP [10mM] had the same effects on GVBD. Forskolin reversed the SNP [10-5M] stimulated meiotic maturation. These results suggest that differences in pathways are present between SNP-inhibited spontaneous meiotic maturation and SNP-stimulated meiotic maturation in mouse oocytes

effect of folic acid on plasma zinc concentration in female rats

Considering the relation of teratogenecity with decreased plasma zinc level and expression of hypotheses concerning effect of folic acid on absorption of zinc, this study was designed to deal with the effect of folic acid on plasma zinc concentration in female rats. In this experimental study we assigned 12 albino rats randomly in 2 groups [6 rats in each group]. The rats had been bred in equal environmental and nutritional slates. Control and experimental groups received intra-peritoneal injections of normal saline 4 CC/Kg and folic acid 4 Mg/Kg respectively. All the rats were beheaded and plasma zinc concentration was measured by use of flameless atomic absorption method. Quantitative data presented as Mean +/- SD, were analyzed by means of T-test. Mean plasma zinc levels in the experimental and control groups were 27.90 +/- 2.23, and 42.1 +/- 0,579 respectively [p=0.000] [t=15.14]. These results indicate that intra-peritoneal injection of folic acid decreases plasma zinc concentration in rats. This adverse effect of folic acid may play a role in the development of congenital defects. Therefore we believe that administration of zinc during pregnancy is at least as important as the administration of folic acid, to prevent occurrence of congenial anomalies