Insulin administration in vivo increases 1,2-diacylglycerol in rat skeletal muscle.

Based on in vitro studies, an insulin-mediated increase in muscle 1,2-diacylglycerol (DAG) content has been proposed as a signal for the insulin induced stimulation of glucose transport. A recent study [Turinsky, J., Bayly, B.P. and O'Sullivan, D.M. (1990) J. Biol. Chem. 265, 7933-7938] challenged this hypothesis because no increase in muscle 1,2-diacylglycerol was observed after in vivo infusions of insulin at doses which markedly stimulated muscle glucose transport. We observed a 30-45% increase in DAG in rat gastrocnemius and diaphragm muscles, 5-15 min after intramuscular or intravenous injections of 1-3 U of insulin per rat, doses which would be expected to activate insulin receptors more fully. The effects on DAG were similar whether or not hypoglycemia was prevented by co-injection of glucose.