Journal article
The effect of inorganic phosphate on the ATP hydrolysis rate and the tension transients in chemically skinned rabbit psoas fibers
Pflügers Archiv, Vol.408(1), pp.1-9
1987
DOI: 10.1007/BF00581833
PMID: 3822768
Abstract
The role of orthophosphate ions (Pi) in crossbridge kinetics was investigated by parallel measurements of the ATP hydrolysis rate and tension transients in maximally activated, chemically skinned rabbit psoas fibers. The hydrolysis rate of the standard activation at 20 degrees C was measured at 1.25 nmole X s-1 X m-1 X fiber-1, which corresponds to the hydrolysis of 3 moles ATP per mole of myosin head per second. The isometric tension, stiffness extrapolated to the infinite frequency, and the ATPase rate progressively decreased when increasing concentrations of Pi (0-16 mM) were added to the activating saline. The decrease was greatest with tension, followed by stiffness and the ATPase rate. Both the apparent rate constant and the magnitude parameters of exponential process (B) increased with Pi concentration resulting in a significant increase in the oscillatory power output. The effects of Pi on processes (A) and (C) were only marginal. When fibers were oscillated at 1 Hz [close to the characteristic frequency of process (A)], no significant increase in the ATP hydrolysis rate was observed. However, a small increase was noticed at 10 Hz [1%, process (B)], and at 100 Hz [6%, process (C)]. We interpret these results in terms of a crossbridge scheme which adds a branch pathway to the conventional hydrolysis cycle. In the proposed scheme, the number of crossbridges entering the branch pathway increases at higher Pi concentrations and in the presence of imposed oscillations at the proper frequency.
Details
- Title: Subtitle
- The effect of inorganic phosphate on the ATP hydrolysis rate and the tension transients in chemically skinned rabbit psoas fibers
- Creators
- M KAWAI - Columbia univ., dep. anatomy cell biology, New York NY 10032, United StatesK GÜTH - Columbia univ., dep. anatomy cell biology, New York NY 10032, United StatesK WINNIKES - Columbia univ., dep. anatomy cell biology, New York NY 10032, United StatesC HAIST - Columbia univ., dep. anatomy cell biology, New York NY 10032, United StatesJ. C RÜEGG - Columbia univ., dep. anatomy cell biology, New York NY 10032, United States
- Resource Type
- Journal article
- Publication Details
- Pflügers Archiv, Vol.408(1), pp.1-9
- Publisher
- Springer; Heidelberg
- DOI
- 10.1007/BF00581833
- PMID
- 3822768
- ISSN
- 0031-6768
- eISSN
- 1432-2013
- Language
- English
- Date published
- 1987
- Academic Unit
- Anatomy and Cell Biology; Internal Medicine
- Record Identifier
- 9984025560402771
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