Volume-regulatory taurine release from a human lung cancer cell line. Evidence for amino acid transport via a volume-activated chloride channel

Exposure of a human lung epithelial cancer cell-line to hypo-osmotic media led to a marked increase in the rate of efflux from the cells of taurine, a non-essential sulfonic amino acid. The osmotically-activated taurine efflux was inhibited by a range of known Cl^- channel blockers, the most potent of which were NPPB and 1,9-dideoxyforskolin. These reagents were similarly effective at inhibiting the osmotically-activated efflux of I^-, a known substrate of volume-activated Cl^- channels. The results are consistent with the hypothesis that volume-regulatory taurine release from these cells is mediated by a volume-activated Cl^- channel.