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Regulation of changes in cytosolic Ca 2+ and Na + concentrations in rat submandibular gland acini exposed to carbachol and ATP
Author(s) -
Hurley Thomas W.,
Ryan Martin P.,
Moore William C.
Publication year - 1996
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199608)168:2<229::aid-jcp1>3.0.co;2-r
Subject(s) - carbachol , extracellular , ionomycin , medicine , endocrinology , ion transporter , chemistry , cytosol , submandibular gland , fura 2 , cotransporter , muscarinic agonist , biophysics , calcium , sodium , intracellular , biology , receptor , biochemistry , membrane , organic chemistry , enzyme
The relationship between cytosolic concentrations of Ca 2+ (Ca i 2 ) and Na + (Na i 2 ) were studied in preparations of rat submandibular and pancreatic acini loaded with the Ca 2+ ‐sensitive dye Fura‐2 or the Na + ‐sensitive dye SBFI. Pancreatic acini showed no changes in Na i 2during either transient or persistent changes in Ca i 2+ . Increases in Ca i 2+produced by exposure of submandibular gland acini to carbachol, a muscarinic cholinergic agonist, were followed by an increase in Na i +after a delay of 5–10 s. When Ca 2+ stores were mobilized without Ca 2+ influx Na i +also increased, but in acini loaded with BAPTA, a nonfluorescent Ca 2+ chelator, the transient increase in Ca 2+ caused by mobilization of stored Ca 2+ was virtually abolished, as was the increase in Na i + . In the presence of ionomycin, increases in Ca i 2+were followed by increases in Na i + . Ca 2+ ‐dependent increases in Na i +were abolished in Na + ‐free buffer and by the presence of furosemide, a blocker of Na + ‐K + ‐2Cl − cotransport. In other studies, extracellular ATP (ATP o ) produced an increase in Ca i 2+and Na i + . The steady‐state increase in Ca i 2+was reduced by increasing extracellular Na + concentrations (Na o + ) in dose‐dependent fashion (IC 50 = 16.4 ± 4.7 mM Na + ). Likewise, increasing Na o +reduced ATP o ‐stimulated 45 Ca 2+ uptake at steady state (IC 50 = 15.8 ± 9.2 mM Na + ). Changing Na o +had no effect on carbachol‐stimulated increases in Ca i 2+ . We conclude that, in rat submandibular gland acini, ATP o promotes an increase in Ca i 2+and Na i +via a common influx pathway and that, under physiologic conditions, Na + significantly limits the ATP o ‐stimulated increase in Ca i 2+ . In the presence of carbachol, however, Na i +rises in Ca i 2+ ‐dependent fashion in submandibular gland acini via stimulation of Na + ‐K + ‐2Cl − cotransport. © 1996 Wiley‐Liss, Inc.