Phospholipase C activation via a GTP-binding protein in tumoral islet cells stimulated by carbamylcholine.

Carbamylcholine and GTP act synergistically in stimulating the production of [3H]inositol-1-phosphate by digitonized tumoral islet cells (RINm5F line) prelabeled with myo-[2-3H(N)]inositol. The response to these two agents is similar to that evoked by GTP gamma S. These findings suggest that a GTP-binding regulatory protein couples the occupancy of muscarinic receptors to activation of phospholipase C in pancreatic islet cells.