Porcine follicular oocytes matured in a modified Krebs-Ringer solution were microinjected with glutathione (GSH) and their male pronucleus (mPN) formation ability was examined after in vitro fertilization. While viability of the oocytes injected with 140 pl vehicle solution (91%) was comparable with non-injected control (93%), microinjections of 35 pl and 140 pl of GSH solution (240 mM) decreased oocyte viability dose dependently (76% and 47%, respectively), showing a toxicity of the highly

more »

... entrated GSH solution. Male PN formation rate was low in the control (23%) and was not affected by injection of vehicle solution (17%). In contrast, a microinjection of both 35 and 140 pl GSH solution increased the ability significantly (52% and 53%, respectively). These rates were, however, significantly lower than the rate (70%) of those matured in porcine follicular fluid, which have been suggested to be comparable with in vivo matured oocytes. These results suggest that the low mPN formation ability in the porcine oocytes matured in vitro might be attributed in part to their low intracellular GSH concentration.