# Relationship between ion currents and membrane capacitance in canine ventricular myocytes

## TL;DR

This study examines how ion currents and membrane capacitance are related in heart cells from dogs, showing that their relationship varies depending on the type of current.

## Contribution

The study provides new statistical evidence on the relationship between ion current parameters and membrane capacitance in canine cardiomyocytes.

## Key findings

- High correlations between Cm and IK1, IKr, and ICa,L were observed under voltage clamp conditions.
- Dividing current parameters by Cm reduced variability and improved normal distribution of the data.
- The correlation between ion currents and Cm depends on the specific current type and cell origin.

## Abstract

Current density, the membrane current value divided by membrane capacitance (Cm), is widely used in cellular electrophysiology. Comparing current densities obtained in different cell populations assume that Cm and ion current magnitudes are linearly related, however data is scarce about this in cardiomyocytes. Therefore, we statistically analyzed the distributions, and the relationship between parameters of canine cardiac ion currents and Cm, and tested if dividing original parameters with Cm had any effect. Under conventional voltage clamp conditions, correlations were high for IK1, moderate for IKr and ICa,L, while negligible for IKs. Correlation between Ito1 peak amplitude and Cm was negligible when analyzing all cells together, however, the analysis showed high correlations when cells of subepicardial, subendocardial or midmyocardial origin were analyzed separately. In action potential voltage clamp experiments IK1, IKr and ICa,L parameters showed high correlations with Cm. For INCX, INa,late and IKs there were low-to-moderate correlations between Cm and these current parameters. Dividing the original current parameters with Cm reduced both the coefficient of variation, and the deviation from normal distribution. The level of correlation between ion currents and Cm varies depending on the ion current studied. This must be considered when evaluating ion current densities in cardiac cells.