Abstract
The purpose of this study was to determine whether 4-chloro-m-cresol (4-CmC) could generate caffeine-like responses in ferret cardiac muscle. The concentration dependence of 4-CmC-mediated release of Ca2+ from the sarcoplasmic reticulum was studied in intact cardiac trabeculae and saponin-skinned fibers in which the sarcoplasmic reticulum was loaded with Ca2+. In intact and saponin-skinned preparations isolated from right ventricle, the effect of 4-CmC on sarcoplasmic reticulum Ca2+ content was estimated by analysis of caffeine contracture after application of chlorocresol. In addition, the effects of 4-CmC on maximal Ca2+-activated tension and the Ca2+ sensitivity of myofibrils were analyzed by using Triton-skinned cardiac fibers. The results show that 4-CmC generates a contractile response in saponin-skinned but not intact fibers. The sarcoplasmic reticulum is implicated in the 4-CmC response; more precisely, in Ca2+ release via the ryanodine receptor. Moreover, 4-CmC, like caffeine, has effects on maximal Ca2+-activated tension and the Ca2+ sensitivity of myofibrils.
Footnotes
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Send reprint requests to: Dr. Stéphanie Choisy, Laboratoire de Physiologie Générale, Centre National de la Recherche Scientifique EP 1593, Faculté des Sciences et des Techniques de Nantes, 3, rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France. E-mail:leoty{at}mailexcite.com
- Abbreviations:
- 4-CmC
- 4-chloro-m-cresol
- Tmax
- maximal tension
- Received November 12, 1998.
- Accepted March 31, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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