NICKEL - AN AGENT FOR INVESTIGATING THE RELATION BETWEEN HORMONE-INDUCED CA2+ INFLUX AND BILE-FLOW IN THE PERFUSED-RAT-LIVER

Influx of Ca2+ induced by the synergistic action of glucagon plus vasopressin in the perfused rat liver was progressively inhibited by infusing increasing concentrations of Ni2+ to the perfusion medium. The onset of Ca2+ influx following vasopressin administration was delayed and inhibition occurred of both the initial rate of Ca2+ influx as well as the total amount of Ca2+ taken up by the liver. Inhibition of the Ca2+ influx rate was almost maximal at approximately 500 mu M Ni2+; half-maximal inhibition occurred at less than 250 mu M. Added Ni2+ also delayed the onset of the early transient bile flow peak. In addition, the duration of the transient peak in bile flow was prolonged by approximately 2 min by all concentrations of Ni2+ between 25-500 mu M, the greatest amount of bile being released in the presence of 250 mu M Ni2+. Concentrations of Ni2+ at 100 mu M and above also inhibit the decrease in bile flow to below baseline levels. The data identify a multiple role for Ca2+ mobilisation in bile flow.