Analysing force-pCa curves

We investigated three forms of the Hill equation used to fit force-calcium data from skinned muscle experiments; Two hyperbolic forms that relate force to calcium concentration directly, and a sigmoid form that relates force to the −log₁₀ of the calcium concentration (pCa). The equations were fit to...

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Veröffentlicht in:Journal of muscle research and cell motility 2010-07, Vol.31 (1), p.59-69
Hauptverfasser: Walker, John S, Li, Xiaotao, Buttrick, Peter M
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Sprache:eng
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Zusammenfassung:We investigated three forms of the Hill equation used to fit force-calcium data from skinned muscle experiments; Two hyperbolic forms that relate force to calcium concentration directly, and a sigmoid form that relates force to the −log₁₀ of the calcium concentration (pCa). The equations were fit to force-calcium data from 39 cardiac myocytes (up to five myocytes from each of nine mice) and the Hill coefficient and the calcium required for half maximal activation, expressed as a concentration (EC₅₀) and as a pCa value (pCa₅₀) were obtained. The pCa₅₀ values were normally distributed and the EC₅₀ values were found to approximate a log-normal distribution. Monte Carlo simulations confirmed that these distributions were intrinsic to the Hill equation. Statistical tests such as the t-test are robust to moderate levels of departure from normality as seen here, and either EC₅₀ or pCa₅₀ may be used to test for significant differences so long as it is kept in mind that [graphic removed] is an additive measure of change and that [graphic removed] is a ratiometric measure of change. The Hill coefficient was found to be sufficiently log-normally distributed that log-transformed values should be used to test for statistically significant differences.
ISSN:0142-4319
1573-2657
DOI:10.1007/s10974-010-9208-7