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Functional ryanodine receptor channels in flatworm muscle fibres

Published online by Cambridge University Press:  01 April 2000

T. A. DAY
Affiliation:
Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA
J. HAITHCOCK
Affiliation:
Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA
M. KIMBER
Affiliation:
Parasitology Research Group, The Queen's University of Belfast, Belfast, Northern Ireland, UK
A. G. MAULE
Affiliation:
Parasitology Research Group, The Queen's University of Belfast, Belfast, Northern Ireland, UK

Abstract

Caffeine, which stimulates intracellular Ca2+ release channels known as ryanodine receptor (RyR) channels, induces contraction of individual muscle fibres dissociated from the trematode Schistosoma mansoni, and the turbellarians Dugesia tigrina and Procerodes littoralis. Caffeine is much more potent on S. mansoni fibres (EC50 0·7 mM) than those from D. tigrina or P. littoralis (3·2 mM and 4·6 mM, respectively). These caffeine-induced contractions are blocked by ryanodine, confirming the presence of functional RyR channels in these flatworm muscles. However, the contractions are not blocked by typical RyR channel blockers ruthenium red or neomycin, indicating that there may be important pharmacological differences between the RyR channels in this early-diverging phylum and those of later animals. These studies demonstrate that RyR channels are present in the muscle of these flatworms, and that the sarcoplasmic reticulum stores sufficient Ca2+ to support contraction.

Type
Research Article
Copyright
2000 Cambridge University Press

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