Ca2+ binding sites in plasma membranes of rat liver and hepatoma cells, and effect of concanavalin A on the Ca2+ binding sites and cellular uptake of Ca2+.
1. Plasma membranes isolated from rat livers and ascites hepatoma cells (AH-130, AH-7974) were assayed for specific Ca2+ binding sites using 45Ca2+ and a Millipore filtration technique. The presence of higher (Kd = 1.4--1.5 . 10(-5) M) and lower (Kd = 0.9--1.0 . 10(-4) M) affinity sites in both liver and hepatoma membranes was observed. The hepatoma plasma membranes however, showed 1.4--2.1-fold as many Ca2+ binding sites (higher and lower affinity sites) as the liver plasma membranes on the basis of protein. 2. Concanavalin A stimulated the specific Ca2+ binding to liver and hepatoma plasma membranes, showing a maximal stimulation (3--5-fold) at 100 microgram/ml. Succinyl concanavalin A was less effective, whereas wheat germ agglutinin and ricinus lectin were ineffective. 3. Concanavalin A stimulated the Ca2+ uptake by AH-7974 cells. The concanavalin A-mediated stimulation of Ca2+ uptake showed lectin-concentrations and Ca2+-concentration dependencies similar to those in the concanavalin A-mediated stimulation of Ca2+ binding.
D000818:Animals; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects; D003208:Concanavalin A / Q000494:pharmacology*; D007700:Kinetics; D037102:Lectins / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D008297:Male; D051381:Rats; D013268:Stimulation, Chemical
D037102:Lectins; D003208:Concanavalin A; D002118:Calcium