INCREASED HEPATIC DELTA-6-DESATURASE ACTIVITY WITH GROWTH-HORMONE EXPRESSION IN THE MG101 TRANSGENIC MOUSE

Growth hormone (GH) has many metabolic effects, but its mechanism(s) o f action are not fully understood. We studied the short-term effects o f endogenously produced GH on liver Delta 6-desaturase activity and ad ipose and liver lipid fraction fatty acid composition in transgenic mi ce. MG101 transgenic mice ages 73-114 d received zinc to activate the ovine GH transgene for 7 d. Nontransgenic littermates, used as control s, also received zinc. Liver lipids were fractionated into phospholipi ds (PL), cholesteryl esters, and triglycerides (TG), and retroperitone al adipose fractionated into PL and TG for fatty acid analysis. Liver microsomes were assayed for Delta 6-desaturase activity. Animals expre ssing the ovine growth hormone transgene had a 2.5-fold higher liver D elta 6-desaturase activity than controls. Arachidonate and docosahexae noate were significantly higher in liver PL of GH transgenic animals c ompared to controls, but both were decreased in adipose PL in the GH a nimals. We conclude that increased production of GH affects both produ ction and organ distribution of highly unsaturated fatty acids, The ch anges in arachidonate in various lipid pools following transgene expre ssion may mediate the systemic actions of GH.