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The Biological Bulletin, Vol 184, Issue 2 209-215, Copyright © 1993 by Marine Biological Laboratory
PHYSIOLOGY |
W. R. Ellington
Department of Biological Science, B-157, Florida State University, Tallahassee, Florida 32306
Myocytes were isolated from the ventricle of the marine clam Mercenaria campechiensis by enzymatic dispersion procedures. Intracellular pH (pHi) was measured via fluorescence imaging techniques using an inverted microscope interfaced with a high sensitivity television camera. Myocyte pHi was similar to values observed in other molluscan muscles measured by weak acid distribution and nuclear magnetic resonance (NMR) techniques. Myocytes displayed a good capacity for defending pHi against changes in extracellular pH (pHe) as the pHi remained unchanged in the pHe range of 7.1 to 8.0, but gradually declined at lower pHe values. Myocytes had a relatively high non-bicarbonate intracellular buffering capacity. Further, these cells showed recovery from imposed acid loads. This recovery was accelerated by increasing HCO3- concentrations, was not dependent on external Na+ and was blocked by a stilbene transport inhibitor, suggesting that a HCO3-:CI- transporter plays a central role in regulation of pHi. Collectively, these data show that ventricular myocytes of M. campechiensis have a relatively high capacity for dealing with potential metabolic proton loads associated with environmental anaerobiosis.
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