Does nitric oxide modulate in vitro maturation of caprine oocytes?

Abstract

The present experiment was conducted to study the effects of nitric oxide (NO) on meiotic maturation of caprine oocytes matured in vitro. Cumulus oocyte complexes (COCs) of excellent and good quality were obtained from slaughterhouse ovaries. COCs were divided into 4 different groups and cultured in tissue culture medium 199 (TCM1999) with 10% v/v estrous goat serum (EGS) over granulosa cell monolayer (GCM) (control), with the addition of 0.04 mM sodium nitroprusside (SNP treatment), 0.6 mM N-nitro L-agrinine methyl ester (L-NAME treatment) and llgl ml of haemoglobin (Hb treatment) at 38±loC and 5% CO2 in humidified atmosphere for 27 h. After 27 h maturation, COCs from 4 groups were taken, sun'ounding cumulus cells were removed and oocytes were fixed in acetic acid and methanol (3: 1) for a least 24h. These oocytes were stained with 1% vlv aceto-orcein in 45% acetic acid and examined under phase contrast microscope (x400) to know the nuclear status. The nuclear study indicated that significantly better maturation was achieved in Hb treatment (87.53%) as compared to control (82.72%), SNP (65.68%) and L-NAME (60.95%) treatment as was evident by the metaphase-II stage. In SNP and L-NAME treatments, significantly lower number of oocytes reached to M II stage than control. But there was an insignificant difference between SNP and LNAME treatments. These findings indicate that both excess NO or inhibition of endogenous NO is detrimental for meiotic maturation. Addition ofHb neutralizes the toxic effects without altering basal synthesis ofNO and has beneficial effects on meiotic maturation.