Sustained diacylglycerol formation in norepinephrine-stimulated rat heart is associated with alpha 1-adrenergic receptor.

We measured the amount of 1,2-diacylglycerol (DG) in rat hearts using thin-layer chromatography and a flame ionization detection technique, since 1,2-DG is thought to play a central role in the metabolism of phosphoinositide hydrolysis. In response to exogenous norepinephrine, a significant increase in 1,2-DG content in the myocardium was observed over 10-60 min, achieving an 80% increase over unstimulated controls at 60 min. On the other hand, the cholesterol content and six species of phospholipids were not significantly affected. In order to elucidate the mechanism of 1,2-DG accumulation elicited by norepinephrine, alpha- and beta-adrenergic antagonists were given. Pretreatment with phentolamine and prazosin, but not propranolol, inhibited the norepinephrine-induced 1,2-DG accumulation. Yohimbine appeared to have a partially inhibitory effect. These results suggest that myocardial norepinephrine-related 1,2-DG formation, which is likely to activate protein kinase C, is associated with alpha-adrenergic receptors, especially alpha 1-adrenergic receptors.