1. The role of protein tyrosine phosphorylation and of G proteins in the activation of a swelling-activated Cl- current (I(Cl,swell)) in calf pulmonary artery endothelial (CPAE) cells was studied using the whole-cell patch clamp technique. I(Cl,swell) was activated by reducing the extracellular osmolality by either 12.5% (mild hypotonicity) or 25% (strong hypotonicity). 2. The protein tyrosine kinase (PTK) inhibitors tyrphostin B46, tyrphostin A25 and genistein inhibited I(Cl,swell) with IC50 values of, respectively, 9.2 ± 0.2, 61.4 ± 1.7 and 62.9 ± 1.3 μM. Tyrphostin A1, a tyrphostin analogue with little effect on PTK activity, and daidzein, an inactive genistein analogue, were without effect on I(Cl,swell). 3. The protein tyrosine phosphatase (PTP) inhibitors Na3VO4 (200 μM) and dephostatin (20 μM) potentiated I(Cl,swell) activated by mild hypotonicity by 47 ± 9 and 69 ± 15%, respectively. 4. Intracellular perfusion with GTPγS (100 μM) transiently activated a Cl- current with an identical biophysical and pharmacological profile to I(Cl,swell). This current was inhibited by the tested PTK inhibitors and potentiated by the PTP inhibitors. Hypertonicity-induced cell shrinkage completely inhibited the GTPγS-activated Cl- current. 5. Intracellular perfusion with GDPβS (1 mM) caused a time-dependent inhibition of I(Cl,swell) which was more pronounced when the current was activated by mild hypotonicity. G. Our results demonstrate that the activity of endothelial swelling-activated Cl- channels is dependent on tyrosine phosphorylation and suggest that G proteins regulate the sensitivity to cell swelling.
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Voets, T., Manolopoulos, V., Eggermont, J., Ellory, C., Droogmans, G., & Nilius, B. (1998). Regulation of a swelling-activated chloride current in bovine endothelium by protein tyrosine phosphorylation and G proteins. Journal of Physiology, 506(2), 341–352. https://doi.org/10.1111/j.1469-7793.1998.341bw.x