To study the biological and morphological characters of bovine mammary epithelial cells in response to heat stress, the cells were exposed to temperatures from 37 ℃to 41℃ for 1 hour, and the cell activities and morphological characters were measured by MTT, trypan blue dying, transmission microscopy, and flow cytometry. Results were shown as follows: (1) Cell proliferation was inhibited. The cell number in the treatment groups was significantly lower than that in the control(P<0.05). During the recovery period, 6-18 hours at 37 ℃ after treatment,the cell numbers were lower and mitotic phases were shorter in heat-treated groups (treated for more than 5 days)than those in the control group(P<0.05). (2)In response to heat stress, the mammary cell nuclei shrank and splintered,the organelles deformed and vacuolated, and the damaged cells developed into apoptosis bodies.(3)By flow cytometric analysis,the numbers of mammary cells arrested at G2 phase after heat shock was significantly higher than in controls(P<0.01). It is concluded that heat stress inhibites mammary epithelial cell proliferation and induces cell apoptosis.
