Expression of skin color genes in lymphocytes of Karan Fries cattle and seasonal relationship with tyrosinase and cortisol.

To evaluate difference in the expression of skin color genes (melanocortin 1 receptor (MC1R) and premelanosome (PMEL)) in lymphocytes during winter and summer season and their correlation with tyrosinase enzyme and cortisol, ten Karan-Fries heifers were selected from National Dairy Research Institute (NDRI) cattle farm. Blood samples were collected from the animals during winter (THI = 60) and summer (THI = 83) season at weekly intervals. Relative MC1R and PMEL messenger RNA (mRNA) expression of Karan Fries cattle was found to be significantly (P < 0.01) higher during winter than summer. Similarly, tyrosinase activity during winter was found to be significantly (P < 0.01) higher than summer season. However, plasma cortisol level was significantly (P < 0.01) higher during summer than winter. Thus, expression of the skin color genes showed positive correlation with tyrosinase enzyme, but negative correlation with cortisol level. Expression of MC1R and PMEL in lymphocytes and tyrosinase activity of Karan Fries cattle was highly reduced during summer. The present study showed that the ability of Karan Fries cattle to protect themselves from the harmful radiation of sunlight by melanization decreased with increased heat stress on them.