Effect of insulin and prolactin on acyltransferase activities in MAC-T bovine mammary cells.

The enzymatic activities of sn-glycerol-3-phosphate acyltransferase and lysophosphatidate acyltransferase were investigated in microsomal fractions prepared from MAC-T cells from bovine mammary gland and from FTO-2B cells from rat liver. In both cell lines, sn-glycerol-3-phosphate acyltransferase exhibited similar rates of palmitate and oleate incorporation. However, lysophosphatidate acyltransferase activity in MAC-T cells had a 2.8-fold greater rate of palmitate incorporation than of oleate incorporation. In FTO-2B cells, there was a 1.4-fold greater rate of oleate incorporation than of palmitate incorporation. FTO-2B and MAC-T cells displayed acyltransferase activities that were consistent with liver and mammary tissues, respectively. The acyltransferases were examined from FTO-2B and MAC-T cells that were treated with insulin and prolactin. Insulin suppressed both acyltransferase activities in FTO-2B cells, and prolactin had a stimulatory effect; however, these effects were very small. In contrast, insulin and prolactin had a stimulatory effect on both acyltransferase activities in MAC-T cells; prolactin elicited the largest effect. Treatment of MAC-T cells with cycloheximide inhibited the stimulatory effect of prolactin on acyltransferase activities.