[Modeling changes in the muscle fiber T-system during direct current flow]

Quantitative calculations of the dynamics of changes in K+, Na+, and Cl- concentrations in the T-system (TS) with changeable volume have been made using the computer "Dniepr-24". It was assumed that the current is transferred throught the TS membrane by K+ and in the lumen of the TS by K+, Na+ and Cl- ions in accordance with their mobilities and concentrations. The model predicts the accumulation of salt and water in the TS at the site of outgoing current. The swelling of TS due to DC effect according to the model was found to be about 9 and 18% for the current densities of 0.39 X 10(-8) a- cm-2 and 2.34 X 10(-8) a-cm-2, resp. The model shows that changes in the ion concentration and in the TS volume with current densities used experimentally reach a steady-state level. The increase of the current by almost 4 times, according to the model, suggests some disturbance in the steady-state and in the TS swelling comparable with experimental observations of vacuole formation.