Heat shock impairs DNA synthesis and down-regulates gene expression for leptin and Ob-Rb receptor in concanavalin A-stimulated bovine peripheral blood mononuclear cells.

This study verified whether leptin or its long isoform receptor (Ob-Rb) genes are expressed in proliferating lymphocytes from bovine species, and whether their expression changes with increased temperatures. Peripheral blood mononuclear cells (PBMC) from five Holstein cows were incubated in the presence of concanavalin A, and alternatively subjected for 65 h to each of the following treatments (T): 39 degrees C continuously (T39) or three 13-h cycles at 40 (T40), 41 (T41) or 42 degrees C (T42), respectively, which were alternated with two 13-h cycles at 39 degrees C. T39 mimicked normothermia; T40, 41 and 42 mimicked conditions of hyperthermia alternated with normothermia. PBMC proliferation declined under T42. Compared with T39, levels of mRNA for leptin was lower under T42, whereas mRNA for Ob-Rb was lower in lymphocytes cultured both under T41 and T42. DNA synthesis was positively correlated with leptin mRNA. This study supports the concept that severe heat stress impairs proliferation of bovine PBMC, confirms that bovine lymphocytes express Ob-Rb gene, and provides the first experimental evidence that bovine lymphocytes express gene for leptin, and that increased temperatures are associated with altered gene expression for leptin and Ob-Rb.