Abstract.
Two Chinese hamster ovary cell (CHO-K1) mutants selected for defective glutamate transport via system X− AG are also highly permeable to small neutral molecules. Light microscopy demonstrated that exposure of one of these mutants, Ed-A1, to hypo-osmotic medium led to extremely rapid swelling, presumably due to increased water flux. When placed in 20% saline, Ed-A1 cells swelled to three times their original volume within 15 sec, a sixfold larger increase than parental CHO-K1. In spite of this rapid volume increase, mutant and wild-type cells remained viable for 20 min in dilute saline. A regulatory volume decrease in Ed-A1, and the continual swelling of CHO-K1, resulted in the two cells achieving equal size after 5 min in 20% saline.
The time course of these volume changes permitted analysis of large numbers of cells by a hydrodynamic technique, steric field flow fractionation (FFF). Steric FFF demonstrated the expected inhibition of osmotic swelling of human erythrocytes by the mercurial, p-chloromercuribenzenesulfonic acid (PCMBS). However, PCMBS increased the apparent swelling rate of Ed-A1 and CHO-K1, suggesting that an aquaporin-like molecule is not responsible for any significant fraction of the water fluxes into either line. PCMBS also strongly inhibited aspartate transport by system X− AG. By taking advantage of their different swelling rates in hypotonic medium, steric FFF can separate mixtures of CHO-K1 and Ed-A1.
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Received: 2 August 1996/Revised: 25 October 1996
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Tong, X., Ash, J. & Caldwell, K. Rapid Swelling of a CHO-K1 Aspartate/Glutamate Transport Mutant in Hypo-osmotic Medium . J. Membrane Biol. 156 , 131 –139 (1997). https://doi.org/10.1007/s002329900195
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DOI: https://doi.org/10.1007/s002329900195