Activation by acidic pH of CLC-7 expressed in oocytes from Xenopus laevis

CIC chloride channels are important in diverse physiological functions such as transepithelial transport, cell volume regulation, excitability, and acidification of intracellular organelles. We have investigated the expression of CLC-7 in oocytes from Xenopus laevis with the two electrode voltage clamp technique and Western blot analysis. Using a specific antibody against CLC-7, we found an approximate to80 kDa protein in oocytes, previously injected with CLC-7-cRNA. In voltage clamp experiments on CIC-7-cRNA-injected oocytes, no current changes were detected at normal pH (7.4). However, acidification of the Ringer solution to pH values between 6 and 4 revealed strong currents which reversed at about -15 mV (30 mV positive to the normal resting potential) and showed strong outward rectification. We therefore suggest that CIC-7 in oocytes is a functional chloride current at acidic p. Since CIC-7 is also found in neuronal tissues and was upregulated in a rat pain model, we suggest a role of CLC-7 also for nociception and pain. (C) 2002 Elsevier Science (USA).