Potentiation of the glycogenolytic and haemodynamic actions of adenosine in the perfused rat liver by verapamil.

The effects of calcium channel blockers on the glycogenolytic and haemodynamic responses to adenosine were determined in perfused rat liver. Verapamil, 5-25 microM, potentiated the increased glucose output and vasoconstriction observed in response to adenosine. In the absence of perfusate calcium, adenosine responses were inhibited and verapamil was without effect. Verapamil did not potentiate the elevation of hepatic cAMP observed in response to a sub-maximal adenosine concentration (15 microM). In contrast to verapamil, nifedipine, 5 microM, was without effect on hepatic responses to adenosine. It is concluded that the potentiating effects of verapamil on hepatic responses to adenosine may be unrelated to the calcium-channel blocking activity of the compound