Diacylglycerol production induced by growth hormone in OB1771 preadipocytes arises from phosphatidylcholine breakdown

Growth Hormone has recently been shown to stimulate the formation of diacylglycerol in Ob1771 mouse preadipocyte cells without increasing inositol lipid turnover (ref. 17). Addition of growth hormone to Ob1771 cells prelabelled with [ 3H]glycerol or [ 3H]choline led to a rapid, transient and stoechiometric formation of labelled diacylglycerol and phosphocholine, respectively. In contrast, no change was observed in the level of choline and phosphoatidic acid whereas the release of water-soluble metabolites in [ 3H]ethanolamine prelabelled cells exposed to growth hormone was hardly detectable. Stimulation by growth hormone of cells prelabelled with (2-palmitoyl 9,10 [ 3H])phosphatidylcholine also induced the production of labelled diacyglycerol. Pertussis toxin abolished both diacylglycerol and phosphocholine formation induced by growth hormone. It is concluded that growth hormone mediates diacylglycerol production in Ob1771 cells by means of phosphatidylcholine breakdown involving a phospholipase C which is likely coupled to the growth hormone receptor via a pertussis toxin-sensitive G-protein.