Effects of caffeine and cyclopiazonic acid on contractile proteins of adult and newborn ferret cardiac fibres.
Ventricular trabeculae from adult and newborn ferret heart were chemically skinned by Triton X-100 which disrupts all cellular membranes. In newborn preparations, maximal Ca(2+)-activated tension was two times smaller than in adult fibres while Ca2+ sensitivity was higher. Caffeine (10 mM) and cyclopiazonic acid (100 and 200 microM) increased the Ca2+ sensitivity in the two groups of preparations. The caffeine effects were more pronounced in adult than in newborn fibres while the cyclopiazonic acid effects were larger in newborn preparations. In the presence of both drugs. the increase of Ca2+ sensitivity was equal to the addition of the effect of each drug applied separately. These results suggest that the drugs act on two different binding sites. Consequently, care must be taken when caffeine and cyclopiazonic acid are used to study the function of the sarcoplasmic reticulum in intact or saponin-skinned fibres.
Bonnet
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Laboratoire de Physiologie Générale, URA CNRS 1340, Faculté des Sciences et des Techniques, Nantes, France.
Léoty
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D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D003285:Contractile Proteins / Q000187:drug effects / Q000502:physiology*; D005289:Ferrets; D006321:Heart / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D006352:Heart Ventricles; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology*; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000502:physiology; D009200:Myocardial Contraction / Q000187:drug effects*
D000889:Anti-Arrhythmia Agents; D003285:Contractile Proteins; D007211:Indoles; D002110:Caffeine; D002118:Calcium; C000543:cyclopiazonic acid