Inhibition of adenosine mediated responses in isolated hepatocytes by depolarizing concentrations of K+

Isolated rat hepatocytes, incubated in a high K+ medium which depolarizes their plasma membrane, were used to investigate the response to adenosine. High K+ concentration blocked both the adenosine mediated increase of calcium influx and the increase in the rate of urea synthesis. It is concluded that a) adenosine stimulates calcium influx in hepatocytes probably through receptor-operated Ca2+ channels which are closed by depolarization of the plasma membrane, b) the higher cytosolic calcium concentration triggers a regulatory step that fully stimulates the rate in urea synthesis.