Volume-activated osmolyte channel in skate erythrocytes: Inhibition by pyridoxal derivatives

Abstract

Volume expansion of erythrocytes of little skate, Raja erinacea, triggers the opening of an osmolyte channel. We review this transport mechanism and further investigate the channel's physicochemical nature by probing the channel with a series of pyridoxine derivatives in skate RBC as well as in epithelial cells: MDCK and C6 glioma cells and in skate hepatocytes. The identity of the transport mechanism (band 3 vs. An anion channel) which mediates the swelling‐activated efflux of osmolytes in fish RBC is controversial. Therefore, we compared taurine and Cl– effluxes in similar conditions. We found that there is significant Cl– loss from volume‐expanded skate RBC. However, there was no effect of either hypotonicity or a number of taurine transport inhibitors on this loss. Utilizing changes in intracellular pH as a means of indirectly measuring H+/Cl– cotransport, we found that a rise in cell pH accompanied the loss of Cl–. This suggests that Cl– efflux could occur via a H+/Cl– cotransporter. To probe and compare the osmolyte channel (taurine efflux) of the skate RBC and three other cell types we used a family of pyridoxine inhibitors. The inhibitory patterns for the skate erythrocytes and hepatocytes differed from those for MDCK and C6 glioma cells and the two former cell types differed from each other. Therefore, the results show that the osmolyte channel in the skate differs from that in other epithelial cells with regard to pyridoxine derivative binding properties. J. Exp. Zool. 279:456–461, 1997. © 1997 Wiley‐Liss, Inc.

Cell and molecular biology of the spiny dogfish Squalus acanthias and little skate Leucoraja erinacea: insights from in vitro cultured cells

“…The system is particularly useful in studies of transmembrane uptake and efflux in experiments with well‐controlled external environments, such as studies of bile‐salt uptake and identification of the transporter involved, and similar studies of amino‐acid uptake (Shuttleworth & Goldstein, 1984; Fricker et al , 1987, 1994; Smith et al , 1987; Ballatori et al , 1988 a , 1999). The cultures also have been used to characterize chloride and manganese uptake and release (Davis‐Amaral et al , 1996, 1997; Madejczyk et al , 2009). Ultrastructural and functional studies in vitro have shown that the microtubule cytoskeleton is involved in an essential way in transcytosis, endocytosis and bile excretory function (Henson et al , 1995; Miller et al , 1996).…”