Abstract: Pig ovaries collected from the slaughterhouse were divided into heat stress group and control group. Immature oocytes were taken from ovaries in each group. Brilliant cresol blue staining method was used to study glucose\|6\|phosphate dehydrogenase （G6PD） activity of immature oocytes in each group. Hoechst 33342 was used to label DNA and distinguish the chromatin configuration. It was shown that the percentage of BCB+oocyte in heat stress group was significantly lower than that in control group（P＜0.05）. The proportions of chromatin configuration exhibited no significant differences between heat stress group and control group（P＞0.05）. The proportions of GV1 to GV3 had no significant difference between BCB+and BCB\|oocytes（P＞0.05）. In the control group， the proportion of GV4 chromatin configuration was obviously higher in BCB+oocytes than that in BCB-ones（P＜0.05）， but the proportion of GVBD had no significant difference（P＞0.05）. The proportion of GV4 chromatin configuration had no significant difference between BCB+and BCB-in the heat stress group（P＞0.05）， but the proportion of GVBD was obviously lower in BCB+oocytes than that in BCB-（P＜0.05）. In conclusion， the heat stress affected the metabolic activity of porcine immature oocytes， but had little effects on chromatin configuration.

Key words: chromatin configuration, glucose\, 6\, phosphate dehydrogenase （G6PD）, pig oocyte, heat stress