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Studies on muscle cells isolated from Schistosoma mansoni: a Ca2+-dependent K+ channel

Published online by Cambridge University Press:  06 April 2009

K. L. Blair
Affiliation:
Department of Zoology and Department of Pharmacology and Toxicology and the Neuroscience Program, Michigan State University, East Lansing, MI, 48824, USA
T. A. Day
Affiliation:
Department of Zoology and Department of Pharmacology and Toxicology and the Neuroscience Program, Michigan State University, East Lansing, MI, 48824, USA
M. C. Lewis
Affiliation:
Department of Zoology and Department of Pharmacology and Toxicology and the Neuroscience Program, Michigan State University, East Lansing, MI, 48824, USA
J. L. Bennett
Affiliation:
Department of Zoology and Department of Pharmacology and Toxicology and the Neuroscience Program, Michigan State University, East Lansing, MI, 48824, USA
R. A. Pax
Affiliation:
Department of Zoology and Department of Pharmacology and Toxicology and the Neuroscience Program, Michigan State University, East Lansing, MI, 48824, USA

Summary

Muscle cells from adult male Schistosoma mansoni have been isolated using a combination of papain digestions and mechanical dissociation procedures. The muscle fibres isolated in this way lacked nuclei but they did contract and relax in response to high [K+], a response which was blocked in the presence of Co2+. From this we conclude that the isolation procedure yields viable muscle fibres useful for physiological studies. Patch-clamp recordings taken from the isolated fibres show a variety of discrete ionic conductances. In inside-out patches one prominent channel was a Ca2+-activated K+ channel with a conductance of 195 pS and a selectivity greater than 10:1 for K+ over Na+, Cs+ or NH4+. Percentage open time was dependent on [Ca2+] at the intracellular face. With [Ca2+] at 1 μM or greater percentage open time was > 95%; at 0.1 μM it was < 2%. No voltage sensitivity could be detected in the voltage range from –50 to –10 mV membrane potential. Ba2+ (10 mM), but neither tetraethylammonium nor 3,4-diaminopyridine blocked the channel from the intracellular face. This Ca2+-activated K+ channel in the muscle membrane of this acoelomate animal is similar in most respects to the maxi-K+ channels which have been described in a variety of cells from more highly evolved animals.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1991

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