title: Rapid swelling of a CHO-K1 aspartate/glutamate transport mutant in hypo-osmotic medium.
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.
authors.affiliation: Department of Bioengineering, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: X
authors.initials: X
authors.lastname: Tong
authors.forename: J F
authors.initials: JF
authors.lastname: Ash
authors.forename: K D
authors.initials: KD
authors.lastname: Caldwell
mesh_terms: D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000328:Adult; D027322:Amino Acid Transport System X-AG; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D016466:CHO Cells / Q000187:drug effects* / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D048429:Cell Size / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus / Q000235:genetics; D004912:Erythrocytes / Q000187:drug effects; D050491:Glutamate Plasma Membrane Transport Proteins; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D009996:Osmotic Fragility; D009997:Osmotic Pressure; D027981:Symporters
chemical_list: D027322:Amino Acid Transport System X-AG; D002352:Carrier Proteins; D050491:Glutamate Plasma Membrane Transport Proteins; D007038:Hypotonic Solutions; D027981:Symporters; D001224:Aspartic Acid; D018698:Glutamic Acid; D002731:4-Chloromercuribenzenesulfonate