RT Journal Article SR Electronic T1 Interaction of Dibucaine and Calcium Ion on a Calcium Pump Reconstituted from Defined Components of Intestinal Brush Border JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 138 OP 144 VO 14 IS 1 A1 MASARU KUREBE YR 1978 UL http://molpharm.aspetjournals.org/content/14/1/138.abstract AB The uptake of Ca++ by reconstituted proteoliposomes involves an ATP-independent as well as an ATP-dependent process. In the presence of 0.7 mM ATP, 1 mM dibucaine inhibited Ca++ uptake and (Mg++ + Ca++)-ATPase activity, but 0.2 mM dibucaine stimulated both. The latter reduced the velocity of ATP-independent Ca++ uptake at low Ca++ concentrations, but increased it at a high concentration (0.15 mM of Ca++. ATP-dependent Ca++ uptake was facilitated by 0.2 mM dibucaine only in the presence of a high concentration of Ca++. Kinetic analyses of the data obtained with the lower dose of dibucaine suggest that this compound competes with Ca++ for binding sites on the outer surface of membranes and that its interaction with Ca++ induces a conformational change of membranes accompanied by an increase in the passive permeability of Ca++ and activation of the ATP-mediated Ca++ pump.