[Mathematical model of electromechanical coupling in the rat myocardium].

A mathematical modelling approach was used to study the negative staircase in the rat papillary muscle. This phenomenon was found to be associated with an excess of the steady-state Ca++-influx in the myocardium cells. The model with a single chamber intracellular Ca-pool simulates satisfactory the experimental data obtained with a standard set of parameter values. It is concluded that the rat myocardium sarcoplasmic reticulum is loaded by Ca++-ions which enter the cell as a potential-independent Ca-influx presumably.