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The Effects of pH on the Sodium‐Withdrawal Contractures Evoked from Frog Atrial Trabeculae
Author(s) -
Chapman R. A.
Publication year - 1980
Publication title -
quarterly journal of experimental physiology and cognate medical sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0033-5541
DOI - 10.1113/expphysiol.1980.sp002522
Subject(s) - chemistry , muscle contracture , extracellular , sodium , biophysics , egta , perfusion , ammonium chloride , extracellular fluid , calcium , potassium , intracellular , medicine , biochemistry , anatomy , biology , organic chemistry
Contractures can be evoked from frog atrial trabeculae by raising extracellular pH in Na‐free fluid after the spontaneous relaxation of the teision evoked by removineg extracellular Na. These alkalinity contractures are unffected by local anaesthetics but are absent following a brief perfusion with Ca‐free fluid containing EGTA. The application of ammonium chloride produces similar‐contractures which are unaffected by perfusion with Ca‐free fluid but are partially inhibited by local analesthetics. Perfusioni by solution containing a high Pco 2 fails to induce contractures. The relationship between [Na] o and tension is altered by changing extracellur pH: acidic fluids below pH 6·0 reduce tension and alkaline fluids increase tenision over the whole range. NH 4 Cl has the same effect as alkalinc fluids while CO 2 ‐conitaining flid has no effect. These results can be interpreted if the effects of variation of extracelluar pH. on Na‐withdrawa; contractures, are mediated by changes in intracellular pH which in turn affect the Ca‐sensitivity of the contractile proteins.