Effect of heat shock and chemical stress on oocyte maturation:: A comparative study in Xenopus and Rana dybowskii

Response to heat shock is a conserved feature of most of the living cells. Resumption of meotic division of oocyte is associated with a complex signaling cascade during progesterone induced oocyte maturation in amphibians. Experiments were carried out to examine the effect of heat shock (35 degrees C) in progesterone induced oocyte maturation processes of Rana and Xenopus. Preincubation of oocytes at 35 degrees C for 90 min inhibited progesterone induced oocyte maturation (germinal vesicle brlakdown; GVBD) in Rana dybowskii but not in Xenopus. This implies that oocyte maturation process is sensitive to environmental stress. When the oocytes were given heat shock at 35 degrees C for 90 min, there was a sharp decrease (1/6th of control) in protein synthesis following progesterone stimulation (12 h) in Rana, whereas less decrease (1/2 of control) appeared in Xenopus. This study suggests that oocytes of Xenopus and Rana respond in different way to the same environmental stress.