Evidence that lanthanum ions stimulate calcium inflow to isolated hepatocytes.
LaCl3 stimulated the initial rate of 45Ca2+ exchange measured under steady-state conditions in isolated liver cells. Cu2+ greater than La3+ = Fe3+ greater than Fe2+ = Zn2+ greater Ni2+ greater than Mn2+ also stimulated 45Ca2+ exchange. Compartmental analysis of 45Ca2+-exchange curves obtained in the presence or absence of La3+, and in the presence or absence of adrenaline, showed that the predominant effect of La3+ is to stimulate the inflow of Ca2+ to the cell from the medium. No evidence for an inhibition of Ca2+ outflow from the cell was obtained. In the presence of La3+, adrenaline caused no further stimulation of Ca2+ inflow to the cell. In the absence of adrenaline, La3+ increased the uptake of Ca2+ (measured by atomic-absorption spectroscopy) by isolated hepatocytes incubated at 1 degree C. The proposal that La3+ stimulates Ca2+ inflow to the liver cell by inducing a conformational change in the Ca2+-inflow transporter of the plasma membrane is briefly discussed.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002413:Cations, Divalent / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D013268:Stimulation, Chemical
D002413:Cations, Divalent; D007811:Lanthanum; D002118:Calcium; D004837:Epinephrine