Abstract
It is considered that the Cl− flux across the cell membrane is coupled with water movements, and thereby with the cellular volume regulation. To examine this hypothesis in a quantitative manner, we incorporated osmotic water flux as well as the volume regulated Cl− channel (VRCC) and c-AMP activated cystic fibrosis transmembrane conductance regulator (CFTR) channel into the "Kyoto-model", a mathematical ventricular cell model. The passive Cl− movement was balanced simply by adding Na+-K+-2Cl− cotransporter (NKCC), neglecting other types of Cl− transporters and the steady state Cl− concentration was more than 50 mM when stimulated at 2.5 Hz. The model well reconstructed the experimental findings such as, 1) the cell volume decreases in a reversible manner when the CFTR Cl− channel was activated. 2) The cell swelling induced by superfusing the cell with variable osmotic solutions showed volume changes as observed in experiments. 3) During superfusion of 70% hypotonic solution showed little regulatory volume decrease (RVD) with the experimental amplitude of the volume-activated Cl− current. To our knowledge, the present cardiac cell model is the first in including the Cl− homeostasis. [Jpn J Physiol 55 Suppl:S98 (2005)]
