Effects of extracellular pH and D-lactate efflux on regulation of intracellular pH during isotonic contractions in a molluscan muscle: A31p-nuclear magnetic resonance study
✍ Scribed by Wiseman, Robert W. ;Ellington, W. Ross ;Rosanske, R. C.
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 973 KB
- Volume
- 252
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
Isotonic contractions were electrically induced in isolated radula protractor muscles of the whelk Busycon canaliculatum, mounted and superfused under anoxic conditions in a special 5 mm phosphorus nuclear magnetic resonance ( 31P-NMR) probe. 31P-NMR spectra showed that there was a decrease in intracellular pH (pHi) from 7.29 to 7.01 during the time course of 30 min of contractile activity. Subsequent biochemical analysis of the tissue and superfusion medium showed that D-lactate and, to a much lesser extent, alanopine and octopine were the major glycolytic end products. Approximately 75% of the total D-lactate produced was released into the medium. When the superfusate pH was changed from 7.8 to 1.2, a much more pronounced intracellular acidification took place, as the pHi fell to 6.80. However, there was no significant effect on the extent of release of D-lactate from the muscle. Elevation of the superfusate pH to 8.2 had no significant. effect on final pHi or D-lactate efflux. D-lactate efflux was reduced when acyanohydroxycinnamic acid or L-lactate was added to the superfusate at pH 7.8. These treatments had no significant effect on the final pHi. Movement of proton equivalents and D-lactate efflux are not tightly linked in this muscle system.