Extracellular Mg2+ regulates the intracellular Na+ concentration in rat sublingual acini.
The intracellular free Na+ concentration ([Na+]i) increases during muscarinic stimulation in salivary acinar cells. The present study examined in rat sublingual acini the role of extracellular Mg2+ in the regulation of the stimulated [Na+]i increase using the fluorescent sodium indicator benzofuran isophthalate (SBFI). The muscarinic induced rise in [Na+]i was approximately 4-fold greater in the absence of extracellular Mg2+. When Na+ efflux was blocked by the Na+,K+-ATPase inhibitor ouabain, the stimulated [Na+]i increase was comparable to that seen in an Mg2+-free medium. Moreover, ouabain did not add further to the stimulated [Na+]i increase in an Mg2+-free medium suggesting that removal of extracellular Mg2+ may inhibit the Na+ pump. In agreement with this assumption, ouabain-sensitive Na+ efflux and rubidium uptake were reduced by extracellular Mg2+ depletion. Our results suggest that extracellular Mg2+ may regulate [Na+]i in sublingual salivary acinar cells by modulating Na+ pump activity.
Zhang
G H
GH
Department of Dental Research, University of Rochester Medical Center, NY 14642, USA.
Melvin
J E
JE
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D008274:Magnesium / Q000378:metabolism*; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013361:Sublingual Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D018721:Muscarinic Agonists; D010042:Ouabain; D002217:Carbachol; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D012413:Rubidium