This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.105.062828v1 89/3/2170    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Zaniboni, M. Articles by Groppi, M. Search for Related Content PubMed PubMed Citation Articles by Zaniboni, M. Articles by Groppi, M.

Effect of Input Resistance Voltage-Dependency on DC Estimate of Membrane Capacitance in Cardiac Myocytes

M. Zaniboni ^*, F. Cacciani ^* and M. Groppi 

^* Dipartimento di Biologia Evolutiva e Funzionale-Sezione Fisiologia, and Dipartimento di Matematica, Università degli Studi di Parma, Parma, Italy

Correspondence: Address reprint requests to M. Zaniboni, Tel.: 05-21-905623; E-mail: zaniboni{at}biol.unipr.it.

The measure of membrane capacitance (C_m) in cardiac myocytes is of primary importance as an index of their size in physiological and pathological conditions, and for the understanding of their excitability. Although a plethora of very accurate methods has been developed to access C_m value in single cells, cardiac electrophysiologists still use, in the majority of laboratories, classical direct current techniques as they have been established in the early days of cardiac cellular electrophysiology. These techniques are based on the assumption that cardiac membrane resistance (R_m) is constant, or changes negligibly, in a narrow potential range around resting potential. Using patch-clamp whole-cell recordings, both in current-clamp and voltage-clamp conditions, and numerical simulations, we document here the voltage-dependency of R_m, up to –45% of its resting value for 10-mV hyperpolarization, in resting rat ventricular myocytes. We show how this dependency makes classical protocols to misestimate C_m in a voltage-dependent manner (up to 20% errors), which can dramatically affect C_m-based calculations on cell size and on intracellular ion dynamics. We develop a simple mechanistic model to fit experimental data and obtain voltage-independent estimates of C_m, and we show that accurate estimates can also be extrapolated from the classical approach.

This article has been cited by other articles:

				M. Zaniboni, F. Cacciani, and N. Salvarani Heart/Cardiac Muscle: Temporal variability of repolarization in rat ventricular myocytes paced with time-varying frequencies Exp Physiol, September 1, 2007; 92(5): 859 - 869. [Abstract] [Full Text] [PDF]