Effect of thermal stress on expression profile of apoptosis related genes in peripheral blood mononuclear cells of transition Sahiwal cow.

The study was conducted to evaluate the effect of thermal stress on expression profile of genes related to apoptosis in peripartum Sahiwal cows. For this, twelve pregnant dry Sahiwal cows were selected from Livestock Research Centre at National Dairy Research Institute, Karnal. The cows were divided into two groups consisting of six Sahiwal cows each. Cows of group I calved during thermoneutral temperature conditions (THI=67.3) and cows of group II calved in summer season (THI=79.9). Blood samples were collected on -15, 0 and +15 days with respect to calving where day '0' represents the day of calving. The peripheral blood mononuclear cells (PBMC) were separated and total RNA was isolated for the BCL-2 (B-Cell Lymphoma-2), BAX (BCL-2 antagonist killer-1), BAK (Bcl-2-associated X protein), CASP-3 (cysteine-aspartic proteases-3) and P53 (tumour protien-53) mRNAs expression. It was found that there was up regulation of CASP-3 on the day of calving during both temperature conditions. Comparison between the two temperature conditions showed that expression of CASP-3, BCL-2, BAK, P53 and ratio of BAX/BCL-2 in PBMC increased during summer as compared to thermoneutral condition suggesting the susceptibility of these cells to apoptosis. Based on the above findings it can be concluded that during calving PBMC are more susceptible to apoptosis, and summer being more stressful potentiates the apoptosis of PBMC in Sahiwal cows.