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The role of the sarcolemmal Ca2 + ‐ATPase in the pH transients associated with contraction in rat smooth muscle
Author(s) -
Naderali E. K.,
Buttell N.,
Taggart M. J.,
Bullock A. J.,
Eisner D. A.,
Wray Susan
Publication year - 1997
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1997.329bb.x
Subject(s) - extracellular , intracellular , intracellular ph , contraction (grammar) , chemistry , biophysics , carbachol , muscle contraction , atpase , depolarization , ion transporter , membrane potential , biochemistry , endocrinology , membrane , biology , receptor , enzyme
1 We have investigated the origin of the intracellular acid pH transients that accompany myometrial contraction. Intra‐and extracellular pH were measured with SNARF and intra‐cellular Ca 2+ concentration ([Ca 2+ ] i ) with indo‐1. 2 An intracellular acidification accompanied spontaneous contractions and those elicited by KC1 depolarization or the addition of the agonists carbachol or prostaglandin F 2x . The size of the acidification increased with the magnitude of the contraction. 3 The intracellular acidification was accompanied by an extracellular alkalinization , showing that it results from proton movement across the surface membrane. Furthermore, it was decreased either by addition of Cd 2+ (20 n m , an inhibitor of the sarcolemmal Ca 2+ ‐ATPase) or by elevating [Ca 2+ ] o . 4 Extracellular alkalinization increased the magnitude of the rise of [Ca 2+ ]j and force produced by KC1. 5 An intracellular acidification was also associated with contraction in the portal vein and ureter. 6 We conclude that the sarcolemmal Ca 2+ ‐ATPase produces a significant intracellular acidification while removing Ca 2+ . Both the acidification and decrease of [Ca 2+ ] i will promote relaxation. Since Ca 2+ and protons have opposite effects on many cellular processes, this dual regulation by these two ions may be of general importance.