ISSN:
1573-2657
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary A method for the continuous measurement of ATP hydrolysis (ATPase) by demembranated muscle fibres has been applied to isometrically held, glycerol-extracted flight muscle fibres from the water-bugLethocerus, under conditions of high MgATP, neutral pH, and varying ionic strength, Ca2+ and extension. These variables caused parallel changes in isometric tension and ATPase. The slope of ATPase upon tension (ΔATPase/ΔTension; incremental tension cost) remained the same upon extension at either different Ca2+ concentrations or different ionic strength. Isometric activation by Ca2+ gave a higher incremental tension cost. The calculated mechanical rate constant of the work-producing process, measured by the small-amplitude behaviour, was increased by either Ca2+ or ionic strength, and little changed by extension; there was therefore a dissociation between its value and that of the incremental tension cost. The results appear to exclude a two-state crossbridge model for fibrillar insect flight muscle.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00713058
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