Inhibitory effects of pentacaine and some related local anaesthetics on rat hepatic adenylate cyclase.

In the present study effects of a new local anaesthetics, pentacaine (trans-2-pyrolidinocyclohexylester of 3-pentyloxyphenylcarbamic acid), and of some chemically related compounds on rat hepatic adenylate cyclase activity were studied under various experimental conditions. As compared with tetracaine, the local anaesthetics tested showed stronger inhibitory effects, regardless of the type of stimulating agents used to activate adenylate cyclase. The most potent effect was observed with pentacaine. Its inhibitory effects on glucagon, guanylylimidodiphosphate (Gpp/NH/p), sodium fluoride or forskolin stimulated activity suggest that it may directly act on the catalytic unit of adenylate cyclase. The same conclusion can be drawn based on its inhibitory effects on adenylate cyclase, regardless ATP concentrations used as the enzyme substrate, and on octylpyranoside solubilized enzyme activated by preincubation of the enzyme preparation with Gpp/NH/p. Structure-activity studies have suggested that the pentacaine molecule as a whole and none of its parts alone or its analogs are responsible for the inhibitory effect. However, the inhibitory effects of these compounds on the rat adenylate cyclase activity do not correlate with their local anaesthetic properties. The possibility of using adenylate cyclase inhibitors to decrease cyclic AMP production under pathological conditions, like in cholera, known to be due to a high adenylate cyclase activity, is discussed.