Osmoregulation of taurine efflux from cultured human breast cancer cells: Comparison with volume activated Cl efflux and regulation by extracellular ATP

Shennan, David B. and Thomson, Jean and Gow, Iain F. (2006) Osmoregulation of taurine efflux from cultured human breast cancer cells: Comparison with volume activated Cl efflux and regulation by extracellular ATP. Cellular Physiology and Biochemistry, 18 (1-3). pp. 113-122. ISSN 1015-8987 (http://dx.doi.org/10.1159/000095178)

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Abstract

The properties and regulation of volume-activated taurine efflux from MDA-MB-231 and MCF-7 cells have been investigated. Volume-activated taurine release from both cell lines was almost completely inhibited by diidosalicylate. DIDS, was more effective at inhibiting swelling-induced taurine release from MCF-7 than from MDA-MB-231 cells. On the basis of comparing taurine, Cl- and I- efflux time courses, it appears that volume-activated taurine efflux does not utilize volume-sensitive anion channels in MDA-MB-231 and MCF-7 cells. Extracellular ATP stimulated volume-activated taurine release from MDA-MB-231 cells but not from MCF-7 cells. The effect of ATP was mimicked by UTP and was dependent upon external calcium and inhibited by suramin. However, suramin inhibited volume-activated taurine efflux from both MDA-MB-231 and MCF-7 cells even in the absence of exogenously added ATP suggesting that it acts directly on the taurine efflux pathway and/or is inhibiting the effect of ATP released from the cells. Volume-activated taurine efflux from MDA-MB-231 cells was stimulated by ionomycin. In contrast, ionomycin had no effect on taurine release from MCF-7 cells. Adenosine also stimulated volume-activated taurine efflux from MDA-MB-231 cells. The results suggest that purines regulate taurine transport in MDA-MB-231 cells via more than one type of receptor.

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