title: Evidence for a Na+/Ca2+ exchange mechanism in rat peritoneal mast cells.
abstract: Mast cells lose their ability to secrete when incubated in nominally Ca2+-free medium, but the Na+/K+ pump inhibitor ouabain prevents this loss, suggesting a Na+ dependence of the Ca2+ gradient in rat mast cells. The present study includes measurements of histamine release from cell suspensions, and fura-2/AM and current-clamp experiments on single cells. KB-R7943, an inhibitor of the reverse mode of the Na+/Ca2+ exchanger, 2,4-dichlorobenzamil and La3+ counteracted the increase in histamine release induced by ouabain in a dose-dependent manner. The Ca2+ response to compound 48/80 was reduced by preincubation of the mast cells for 30 min in nominally Ca2+-free medium. This reduction was partly prevented by ouabain or by a low extracellular Na+ concentration. Superfusion of cells with a medium containing a low Na+concentration resulted in a hyperpolarization of the cells of 38.6+/-8.6 mV, n=8, followed by a repolarization after the superfusion had ceased (45.7+/-5.9 mV, n=4). KB-R7943 reduced the hyperpolarization and repolarization induced by a low extracellular Na+ concentration to 15.5+/-2.9 mV (n=7) and 0.2+/-3.4 mV (n=3), respectively. These results are consistent with the presence of a Na+/Ca2+ exchanger in rat peritoneal mast cells.
authors.affiliation: Department of Pharmacology, Odense University, Winsloewparken 19, 5000 Odense C, Denmark. hellep@imbmed.ou.dk
authors.forename: H A
authors.initials: HA
authors.lastname: Praetorius
authors.forename: U G
authors.initials: UG
authors.lastname: Friis
authors.forename: J
authors.initials: J
authors.lastname: Praetorius
authors.forename: T
authors.initials: T
authors.lastname: Johansen
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004553:Electric Conductivity; D006636:Histamine Release / Q000187:drug effects; D007811:Lanthanum / Q000494:pharmacology; D008297:Male; D008407:Mast Cells / Q000502:physiology*; D008564:Membrane Potentials; D010042:Ouabain / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010529:Peritoneal Cavity / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D019831:Sodium-Calcium Exchanger; D010042:Ouabain; D007811:Lanthanum; D000584:Amiloride; C064515:2',4'-dichlorobenzamil amiloride; D012964:Sodium; D002118:Calcium