Journal article
Effect of Ca ion concentration on cross-bridge kinetics in rabbit psoas fibers. Evidence for the presence of two Ca-activated states of thin filament
Biophysical journal, Vol.35(2), pp.375-384
08/1981
DOI: 10.1016/S0006-3495(81)84796-0
PMCID: PMC1327529
PMID: 6791720
Abstract
The effect of Ca ion concentration on cross-bridge kinetics in a small bundle (one to three fibers) of chemically skinned rabbit psoas muscle is studied. The length of the muscle is oscillated in small amplitude sine waves (0.2% L0 peak-to-peak) at varying frequencies (0.125 -- 167 Hz), and the resulting amplitude and phase shift in tension are measured. The frequency response function (complex stiffness) thus obtained can be divided into three parts, which we name process (A) (centered at 1 Hz), process (B) (3--17 Hz), and process (C) (50 Hz). Process (B), which represents oscillatory work, further splits into two processes (B' and B) at partial Ca activation (less than 50% P0), where the phase-frequency plot appears W-shaped. The slower of the two processes (B') disappears by full activation, at which time the plot appears V-shaped. The characteristic frequencies associated with the minima of the plot do not shift in a graded way with Ca concentration, indicating that there is no change in apparent rate constants. Apparent rate constants of processes (A) and (C) are minimally affected by Ca. The above results are not altered when ionic strength is changed between 128 and 265 mM. We propose that activated thin filaments can have two "on" states and that Ca concentration controls the distribution of these two states. This mechanism generally supports the "switch" hypothesis of Ca regulation.
Details
- Title: Subtitle
- Effect of Ca ion concentration on cross-bridge kinetics in rabbit psoas fibers. Evidence for the presence of two Ca-activated states of thin filament
- Creators
- Masakata KawaiRobert N CoxPhilip W Brandt
- Resource Type
- Journal article
- Publication Details
- Biophysical journal, Vol.35(2), pp.375-384
- Publisher
- United States
- DOI
- 10.1016/S0006-3495(81)84796-0
- PMID
- 6791720
- PMCID
- PMC1327529
- ISSN
- 0006-3495
- eISSN
- 1542-0086
- Grant note
- NS11766 / NINDS NIH HHS NS05910 / NINDS NIH HHS AM21530 / NIADDK NIH HHS
- Language
- English
- Date published
- 08/1981
- Academic Unit
- Anatomy and Cell Biology; Internal Medicine
- Record Identifier
- 9984025571102771
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