Tyrosine protein kinase inhibitors prevent activation of cardiac swelling-induced chloride current

The effect of tyrosine protein kinase inhibitors on the swelling-induced chloride current (I-Cl-swelling) of dog atrial myocytes was studied using the whole-cell patch-clamp recording technique. Currents were measured during hyperpolarizing voltage ramps with potassium currents blocked by cesium. Osmolarity was varied using mannitol. Exposure to hypotonic solution (approximate to 249 mosmol/kg) activated I-Cl-swelling. Hypertonic solution (approximate to 363 mosmol/kg) was used to shrink swollen cells and turn off I-Cl-swelling. In studies on the acute effect of tyrosine protein kinase inhibitors each cell was swollen three separate times. Control, treatment, and washout I-Cl-swelling were compared. Genistein (50-80 mu M) prevented reactivation of I-Cl-swelling without affecting cell size. The effect of genistein partially subsided upon washout. The effect of genistein on I-Cl-swelling was not mimicked by 80 mu M daidzein, a related compound that does not inhibit tyrosine protein kinases. When intracellular adenosine 5'-0-(3-thiotriphosphate (ATP[gamma S]) was used, genistein did not prevent the reactivation of I-Cl-swelling. Intracellular ATP[gamma S] did not result in a persistent activation of l(Cl-swelling) when cell size was returned to control. Acute exposure to 1 mu M herbimycin A or 100 mu M tyrphostin 51 did not prohibit the activation of I-Cl-swelling. A 24-h exposure to 1 mu M herbimycin A did inhibit I-Cl-swelling. The results provide important clues regarding the activation mechanism for I-Cl-swelling and suggest that a tyrosine protein phosphorylation may be necessary, but not sufficient, for activation of I-Cl-swelling.