RESUMO
Voltage-dependent, outwardly rectifying anion channels have been described in various cells including lymphocytes. In this study, we found that murine B cells express the voltage-dependent slowly activating anion channels (VSACs). Using a whole-cell configuration, I (VSAC) in Bal-17 was induced by a sustained depolarization (>0 mV) which was remarkably facilitated at 35 degrees C (Q (10)=23 at 30 mV of clamp voltage). Substitution of extracellular Cl(-) with gluconate shifted the reversal potential to the right (35.7 mV). Gd(3+) (IC(50)=0.11 microM) significantly attenuated I (VSAC), but DIDS partially blocked I (VSAC). In addition, extracellular acidification suppressed I (VSAC) whereas alkalinization facilitated the channel activation. I (VSAC) was decreased by 90% at pH 6.35 and increased by 180% at pH 8.0. In cell-attached and inside-out patch clamps, depolarization slowly activated the anion channels of large conductance (approximately 270 pS) with multiple levels of subconductances. The single channel currents were also blocked by Gd(3+) and acidic pH. Furthermore, I (VSAC) was also observed in WEHI-231 (an immature B cell line) and freshly isolated splenic B cells of mice. In summary, murine B cells express unique voltage-dependent anion channels that show a strong sensitivity to both temperature and extracellular pH. Further investigation is required to understand the physiological roles of VSAC and its molecular identity.
