Excitation-contraction coupling in skeletal muscle fibers injected with the InsP3 blocker, heparin.
Heparin, an inhibitor of inositol trisphosphate (InsP3)-induced Ca2+ release in smooth muscle and non-muscle cells, was injected into intact frog skeletal muscle fibres. Ca2+ release from the sarcoplasmic reticulum was elicited by the normal action potential mechanism and monitored by both fura-2 fluorescence and an intrinsic birefringence signal. Both optical signals, and hence Ca2+ release, were unaffected by high concentrations of heparin. This result argues against a major physiological role of InsP3 as a chemical messenger of excitation-contraction coupling in skeletal muscle.
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Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia 19104-6085.
Konishi
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Baylor
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Somlyo
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AP
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism; D005456:Fluorescent Dyes; D016257:Fura-2; D006493:Heparin / Q000494:pharmacology*; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000037:antagonists & inhibitors*; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D011896:Rana temporaria; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013403:Sugar Phosphates / Q000037:antagonists & inhibitors*
D001572:Benzofurans; D005456:Fluorescent Dyes; D007295:Inositol Phosphates; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D002118:Calcium; D016257:Fura-2