SWELLING-ACTIVATED AMINO ACID EFFLUX IN THE HUMAN NEUROBLASTOMA CELL LINE CHP-100. Srisaila Basavappa, Chiun-Chien Huang, Allen W. Mangel, Dmitry V. Lebedev, Philip A. Knauf, and J. Clive Ellory. University Laboratory of Physiology, University of Oxford, Parks Rd., Oxford OX1 3PT, United Kingdom, Glaxo-Wellcome Inc., Research Triangle Park, NC 27709, USA, Department of Biophysics, University of Rochester Medical Center, Rochester, NY, USA.
APStracts 3:0046N, 1996.
SUMMARY AND CONCLUSIONS
1. The effects of hypoosmotic stress on cell volume and amino acid efflux were evaluated in the human neuroblastoma cell line CHP-100 utilizing the Coulter Counter Multisizer and radiolabelled amino acid efflux respectively. 2. CHP- 100 cells swelled by 35% + 5% when the osmolarity of the solution was decreased from 290 to 190 mOsm/kg H 2 O. The rapid swelling was followed by a biphasic regulatory volume decrease (RVD). 3. In cells loaded with 14 C- taurine, hypoosmotic stress induced a 299 + 22% (n=23, p<0.05) increase in taurine efflux compared to controls. This efflux was inhibited by the chloride channel blockers 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), 4,4'- diisothio-cyanostilbene-2,2'-disulfonic acid (DIDS), niflumic acid and by the volume-activated anion channel blocker tamoxifen. In addition, the swelling- activated taurine efflux was dependent upon extracellular calcium. 4. Similarly, in cells loaded with 14 C-glycine, hypoosmotic stress significantly increased glycine efflux, that was also sensitive to NPPB. In contrast, efflux of 3 H-glutamate was not significantly altered following hypoosmotic stress. 5. Using patch clamp recording techniques, Cl - channels were activated in cell attached patches following exposure to hypoosmotic solutions. 6. In nystatin perforated patches, permeability of the hypoosmotically-activated anion channel was observed to be SCN - > I - > Cl - > Br - >> Glu. 7. It is concluded that in CHP-100 cells, anion channels are activated during hypoosmotic stress and these channels represent a pathway for efflux of amino acids. 

Received 3 January 1995; accepted in final form 29 February 1996.
APS Manuscript Number J4-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 20 March 96