Taurine 3 pp 229-235 | Cite as

Taurine Efflux and Intracellular pH during Astrocyte Volume Regulation

  • James E. Olson
  • Robert W. Putnam
  • Julie A. Evers
  • Nicholas Munoz
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 442)


Cytotoxic cerebral edema is characterized by enlarged astroglial cells. In tissue culture, osmotically swollen astrocytes return toward normal volume over a period of 15–30 min in a process termed regulatory volume decrease (RVD). RVD is due, in part, to net efflux of taurine and other amino acids. Our objective in these studies was to examine changes in astrocyte intracellular pH (pHi) which may be related to taurine loss during RVD. We hypothesized net efflux of anionic taurine abandons a proton inside the cell, thus lowering pHi. Primary cultures of cerebral astrocytes were prepared from neonatal rat pups and grown on glass coverslips. Confluent cells were loaded at 37°C with the fluorescent pH indicator BCECF. Fluorescence intensity ratios for excitation wavelengths of 440 nm and 494 nm (530 nm emission) were computed every 2 sec. Intensity ratios were calibrated to pHi at the end of each experiment using 140 mM KCl plus 8.6 μM nigericin at pH 7.4. pHi was measured in isoosmotic Hepes-buffered saline (290 mOsm) and then in hypoosmotic Hepes-buffered saline (200 mOsm) in the presence of 0.5 mM amiloride. Some solutions also contained 150 μM niflumic acid (NA). Cellular taurine content was determined in parallel studies using HPLC. Changes in pHi were compared between groups using Student’s t-test with Bonferroni correction. Significance was assumed if p<0.05. In isoosmotic saline, mean ± SEM pHi was 7.58 ± 0.04 and decreased to 7.35 ± 0.09 after adding amiloride. Hypoosmotic exposure caused a further drop in pHi of 0.29 ± 0.03 within 15 min. Recovery of pHi in isoosmotic saline was amiloride-sensitive. Subsequent hypoosmotic exposure after recovery in isoosmotic saline produced a change in pHi which was 81 ± 9% of the change measured during the initial hypoosmotic exposure. Taurine content decreased from 147 ± 6 nmol/(mg protein) to 116 ± 7 nmol/(mg protein) during the 15 min hypoosmotic exposure in 0.5 mM amiloride. NA significantly reduced the hypoosmotically induced change in pHi to 0.17 ± 0.02 while completely blocking taurine loss. Assuming an intracellular buffering power of 13 mM, the NA-sensitive intracellular acidification of cells during hypoosmotic exposure in the presence of 0.5 mM amiloride corresponds to 1.6 mequiv/l additional intracellular H+. This increase in intracellular H+ content is equivalent to approximately 32% of the NA-sensitive loss of taurine. The association of changes in pHi with taurine efflux is supported by these data; however, efflux of other weak acids may contribute to intracellular acidification during astrocyte RVD and a significant portion of taurine must leave the cell with a proton.


Regulatory Volume Decrease Niflumic Acid Intracellular Acidification Fluorescence Intensity Ratio Taurine Content 
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  1. 1.
    Bender, A.S. and Norenberg, M.D., 1994, Calcium dependence of hypoosmotically induced potassium release in cultured astrocytes, J. Neurosci., 14:4237–4243.PubMedGoogle Scholar
  2. 2.
    Beetsch, J.W. and Olson, J.E., 1996, Hyperosmotic exposure alters total taurine quantity and cellular transport in rat astrocyte cultures, Biochim. Biophys. Acta, 1290:141–148.PubMedCrossRefGoogle Scholar
  3. 3.
    Budavari, S., 1989, The Merck Index, 11th ed., Merck and Company, Rahway, NJ, pp. 1606.Google Scholar
  4. 4.
    Goldstein, L., Davis-Amaral, E.M., and Musch, M.W., 1996, Organic osmolyte channels: Transport characteristics and regulation, Kidney Int., 49:1690–1694.PubMedCrossRefGoogle Scholar
  5. 5.
    Jackson, P.S. and Strange, K., 1993, Volume-sensitive anion channels mediate swelling-activated inositol and taurine efflux, Am. J. Physiol., 265:C1489–C1500.PubMedGoogle Scholar
  6. 6.
    Kimelberg, H.K. and Frangakis, M.V., 1985, Furosemide-and bumetanide-sensitive ion transport and volume control in primary astrocyte cultures from rat brain, Brain Res., 361:125–134.PubMedCrossRefGoogle Scholar
  7. 7.
    Kimelberg, H.K. and O’Connor, E., 1988, Swelling of astrocytes causes membrane potential depolarization, Glia, 1:219–224.PubMedCrossRefGoogle Scholar
  8. 8.
    Lowry, O.H., Rosebrough, N.J., Farr, A.I., and Randall, R.J., 1951, Protein measurement with the Folin phenol reagent, J. Biol. Chem., 193:265–275.PubMedGoogle Scholar
  9. 9.
    O’Connor, E.R. and Kimelberg, H.K., 1993, Role of calcium in astrocyte volume regulation and in the release of ions and amino acids, J. Neurosci., 13:2638–2650.PubMedGoogle Scholar
  10. 10.
    O’Connor, E.R., Sontheimer, H., and Ransom, B.R., 1994, Rat hippocampal astrocytes exhibit electrogenic sodium-bicarbonate co-transport, J. Neurophysiol., 72(6):2580–2589.PubMedGoogle Scholar
  11. 11.
    Olson, J.E. and Goldfinger, M.D., 1990, Amino acid content of rat cerebral astrocytes adapted to hyperosmotic medium in vitro, J. Neurosci. Res., 27:241–246.PubMedCrossRefGoogle Scholar
  12. 12.
    Olson, J.E. and Kimelberg, H.K., 1995, Hypoosmotic volume regulation and osmolyte transport in astrocytes is blocked by an anion transport inhibitor, L-644, 711, Brain Res., 682:197–202.PubMedCrossRefGoogle Scholar
  13. 13.
    Olson, J.E. and Li, G.-Z., 1997, Increased potassium, chloride, and taurine conductances in astrocytes during hypoosmotic swelling, Glia, 20:254–261.PubMedCrossRefGoogle Scholar
  14. 14.
    Olson, J.E., Alexander, C., Feller, D.A., Clayman, M.L., and Ramnath, E.M., 1995, Hypoosmotic volume regulation of astrocytes in elevated extracellular potassium, J. Neurosci. Res., 40:333–342.PubMedCrossRefGoogle Scholar
  15. 15.
    Olson, J.E., Holtzman, D., Sankar, R., Lawson, C., and Rosenberg, R., 1989, Octanoic acid inhibits astrocyte volume control: implications for cerebral edema in Reye’s Syndrome, J. Neurochem., 52:1197–1202.PubMedCrossRefGoogle Scholar
  16. 16.
    Olson, J.E., Sankar, R., Holtzman, D., James, A., and Fleischhaker, D., 1986, Energy-dependent volume regulation in primary cultured cerebral astrocytes, J. Cell. Physiol., 128:209–215.PubMedCrossRefGoogle Scholar
  17. 17.
    Putnam, R.W. and Grubbs, R.D., 1990, Steady-state pHi, buffering power, and effect of CO2 in a smooth muscle-like cell line., Am. J. Physioi., 258:C461–C469.Google Scholar
  18. 18.
    Roy, G. and Banderali, U., 1994, Channels for ions and amino acids in kidney cultured cells (MDCK) during volume regulation, J. Exp. Zool., 268:121–126.PubMedCrossRefGoogle Scholar
  19. 19.
    Sanchez-Olea, R., Morán, J., Schousboe, A., and Pasantes-Morales, A., 1991, Hyposmolarity-activated fluxes of taurine in astrocytes are mediated by diffusion, Neurosci. Lett., 130:233–236.PubMedCrossRefGoogle Scholar
  20. 20.
    Shrode, L.D. and Putnam, R.W., 1994, Intracellular pH in primary rat astrocytes and C6 glioma cells, Glia, 12:196–210.PubMedCrossRefGoogle Scholar
  21. 21.
    Thomas, J.A., Buchsbaum, R.N., Zimniak, A., and Racker, E., 1979, Intracellular pH measurements in Ehrlich ascites tumor cells utilizing spectroscopic probes generated in situ, Biochem. J., 18:2210–2218.CrossRefGoogle Scholar
  22. 22.
    Vitarella, D., DiRisio, D.J., Kimelberg, H.K., and Aschner, M., 1994, Potassium and taurine release are highly correlated with regulatory volume decrease in neonatal primary rat astrocyte cultures, J. Neurochem., 63:1143–1149.PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1998

Authors and Affiliations

  • James E. Olson
    • 1
    • 2
  • Robert W. Putnam
    • 2
  • Julie A. Evers
    • 1
  • Nicholas Munoz
    • 2
  1. 1.Department of Emergency MedicineWright State UniversityDaytonUSA
  2. 2.Department of Physiology and BiophysicsWright State UniversityDaytonUSA

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