Inhibitory effect of barbiturates and local anaesthetics on protein kinase C activation.

A calcium- and phospholipid-dependent protein kinase C subspecies purified from rat brain was inhibited by thiamylal, thiopentone, pentobarbitone, mepivacaine and bupivacaine. This was attributed to the inhibition of the activation process rather than to direct interaction with the active site of the enzyme. It is well established that unsaturated diacylglycerol markedly increases the affinity of protein kinase C for calcium ions. Kinetic analysis suggested that pentobarbitone brought about the inhibition by competing with the diacylglycerol diolein and that mepivacaine and bupivacaine competed with the phospholipid phosphatidylserine used in the assay. The possibility exists that the effects of local anaesthetics on the function of various tissues are due, in part, to an inhibitory action on protein kinase C.