Skip to main content
PMC home page
The Journal of Physiology logoLink to The Journal of Physiology
. 1994 Jan 1;474(1):43–53. doi: 10.1113/jphysiol.1994.sp020001

Sodium-bicarbonate cotransport current in identified leech glial cells.

T Munsch 1, J W Deitmer 1
PMCID: PMC1160294  PMID: 8014897

Abstract

1. The membrane current associated with the cotransport of Na+ and HCO3- was investigated in neuropil glial cells in isolated ganglia of the leech Hirudo medicinalis L. using the two-electrode voltage-clamp technique. 2. The addition of 5% CO2-24 mM HCO3- evoked an outward current, which slowly decayed, and which was dependent upon the presence of external Na+. Removal of CO2-HCO3- elicited a transient inward current. Re-addition of Na+ to Na(+)-free saline in the presence of CO2-HCO3- also produced an outward current. Under these conditions an intracellular alkalinization and a rise in intracellular [Na+] were recorded using triple-barrelled, ion-sensitive microelectrodes. Addition or removal of HCO3-, in the absence of external Na+, caused little or no change in membrane voltage, membrane current and intracellular pH, indicating that the glial membrane has a very low HCO3- conductance. 3. Voltage steps revealed nearly linear current-voltage relationships both in the absence and presence of CO2-HCO3-, with an intersection at the assumed reversal potential of the HCO(3-)-dependent current. These results suggest a cotransport stoichiometry of 2HCO3-: 1 Na+. The HCO(3-)-dependent current could be inhibited by diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS). 4. Simultaneous recording of current and intracellular pH showed a correlation of the maximal acid-base flux with the transient HCO(3-)-dependent current during voltage steps in the presence of CO2-HCO3-. The maximum rate of acid-base flux and the HCO(3-)-dependent peak current showed a similar dependence on membrane voltage. Lowering the external pH from 7.4 to 7.0 produced an inward current, which increased twofold in the presence of CO2-HCO3-. This current was largely inhibited by DIDS, indicating outward-going electrogenic Na(+)-HCO3- cotransport during external acidification. 5. When external Na+ was replaced by Li+, a similar outward current and intracellular alkalinization were observed in the presence of CO2-HCO3-. The Li(+)-induced intracellular alkalinization was not inhibited by amiloride, a blocker of Na+(Li+)-H+ exchange, but was sensitive to DIDS. These results suggest that Li+ could, at least partly, substitute for Na+ at the cotransporter site. 6. Our results indicate that the Na(+)-HCO3- cotransport produces a current across the glial cell membrane in both directions with a reversal potential near the membrane resting potential, rendering pHi a function of the glial membrane potential.

Full text

PDF
43

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Astion M. L., Orkand R. K. Electrogenic Na+/HCO3- cotransport in neuroglia. Glia. 1988;1(5):355–357. doi: 10.1002/glia.440010508. [DOI] [PubMed] [Google Scholar]
  2. Ballanyi K., Schlue W. R. Intracellular chloride activity in glial cells of the leech central nervous system. J Physiol. 1990 Jan;420:325–336. doi: 10.1113/jphysiol.1990.sp017915. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Becker B. F., Duhm J. Evidence for anionic cation transport of lithium, sodium and potassium across the human erythrocyte membrane induced by divalent anions. J Physiol. 1978 Sep;282:149–168. doi: 10.1113/jphysiol.1978.sp012454. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Boron W. F., Boulpaep E. L. Intracellular pH regulation in the renal proximal tubule of the salamander. Basolateral HCO3- transport. J Gen Physiol. 1983 Jan;81(1):53–94. doi: 10.1085/jgp.81.1.53. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Boron W. F., Boulpaep E. L. The electrogenic Na/HCO3 cotransporter. Kidney Int. 1989 Sep;36(3):392–402. doi: 10.1038/ki.1989.208. [DOI] [PubMed] [Google Scholar]
  6. Chow S. Y., Yen-Chow Y. C., White H. S., Woodbury D. M. pH regulation after acid load in primary cultures of mouse astrocytes. Brain Res Dev Brain Res. 1991 May 20;60(1):69–78. doi: 10.1016/0165-3806(91)90156-d. [DOI] [PubMed] [Google Scholar]
  7. Dart C., Vaughan-Jones R. D. Na(+)-HCO3- symport in the sheep cardiac Purkinje fibre. J Physiol. 1992;451:365–385. doi: 10.1113/jphysiol.1992.sp019169. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Deitmer J. W. Bicarbonate-dependent changes of intracellular sodium and pH in identified leech glial cells. Pflugers Arch. 1992 Apr;420(5-6):584–589. doi: 10.1007/BF00374637. [DOI] [PubMed] [Google Scholar]
  9. Deitmer J. W. Electrogenic sodium-dependent bicarbonate secretion by glial cells of the leech central nervous system. J Gen Physiol. 1991 Sep;98(3):637–655. doi: 10.1085/jgp.98.3.637. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Deitmer J. W. Evidence for glial control of extracellular pH in the leech central nervous system. Glia. 1992;5(1):43–47. doi: 10.1002/glia.440050107. [DOI] [PubMed] [Google Scholar]
  11. Deitmer J. W., Schlue W. R. An inwardly directed electrogenic sodium-bicarbonate co-transport in leech glial cells. J Physiol. 1989 Apr;411:179–194. doi: 10.1113/jphysiol.1989.sp017567. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Deitmer J. W., Schlue W. R. The regulation of intracellular pH by identified glial cells and neurones in the central nervous system of the leech. J Physiol. 1987 Jul;388:261–283. doi: 10.1113/jphysiol.1987.sp016614. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Deitmer J. W., Szatkowski M. Membrane potential dependence of intracellular pH regulation by identified glial cells in the leech central nervous system. J Physiol. 1990 Feb;421:617–631. doi: 10.1113/jphysiol.1990.sp017965. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Fitz J. G., Lidofsky S. D., Xie M. H., Scharschmidt B. F. Transmembrane electrical potential difference regulates Na+/HCO3- cotransport and intracellular pH in hepatocytes. Proc Natl Acad Sci U S A. 1992 May 1;89(9):4197–4201. doi: 10.1073/pnas.89.9.4197. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Gray P. T., Ritchie J. M. A voltage-gated chloride conductance in rat cultured astrocytes. Proc R Soc Lond B Biol Sci. 1986 Aug 22;228(1252):267–288. doi: 10.1098/rspb.1986.0055. [DOI] [PubMed] [Google Scholar]
  16. Hughes B. A., Adorante J. S., Miller S. S., Lin H. Apical electrogenic NaHCO3 cotransport. A mechanism for HCO3 absorption across the retinal pigment epithelium. J Gen Physiol. 1989 Jul;94(1):125–150. doi: 10.1085/jgp.94.1.125. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Jentsch T. J., Keller S. K., Koch M., Wiederholt M. Evidence for coupled transport of bicarbonate and sodium in cultured bovine corneal endothelial cells. J Membr Biol. 1984;81(3):189–204. doi: 10.1007/BF01868713. [DOI] [PubMed] [Google Scholar]
  18. Kettenmann H., Schlue W. R. Intracellular pH regulation in cultured mouse oligodendrocytes. J Physiol. 1988 Dec;406:147–162. doi: 10.1113/jphysiol.1988.sp017373. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. La Cour M. Rheogenic sodium-bicarbonate co-transport across the retinal membrane of the frog retinal pigment epithelium. J Physiol. 1989 Dec;419:539–553. doi: 10.1113/jphysiol.1989.sp017885. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Lagadic-Gossmann D., Buckler K. J., Vaughan-Jones R. D. Role of bicarbonate in pH recovery from intracellular acidosis in the guinea-pig ventricular myocyte. J Physiol. 1992 Dec;458:361–384. doi: 10.1113/jphysiol.1992.sp019422. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Munsch T., Deitmer J. W. Calcium transients in identified leech glial cells in situ evoked by high potassium concentrations and 5-hydroxytryptamine. J Exp Biol. 1992 Jun;167:251–265. doi: 10.1242/jeb.167.1.251. [DOI] [PubMed] [Google Scholar]
  22. Newman E. A., Astion M. L. Localization and stoichiometry of electrogenic sodium bicarbonate cotransport in retinal glial cells. Glia. 1991;4(4):424–428. doi: 10.1002/glia.440040411. [DOI] [PubMed] [Google Scholar]
  23. Newman E. A. Sodium-bicarbonate cotransport in retinal Müller (glial) cells of the salamander. J Neurosci. 1991 Dec;11(12):3972–3983. doi: 10.1523/JNEUROSCI.11-12-03972.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Soleimani M., Lesoine G. A., Bergman J. A., Aronson P. S. Cation specificity and modes of the Na+:CO3(2-):HCO3- cotransporter in renal basolateral membrane vesicles. J Biol Chem. 1991 May 15;266(14):8706–8710. [PubMed] [Google Scholar]
  25. Vaughan-Jones R. D. Regulation of chloride in quiescent sheep-heart Purkinje fibres studied using intracellular chloride and pH-sensitive micro-electrodes. J Physiol. 1979 Oct;295:111–137. doi: 10.1113/jphysiol.1979.sp012957. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Walz W., Schlue W. R. External ions and membrane potential of leech neuropile glial cells. Brain Res. 1982 May 6;239(1):119–138. doi: 10.1016/0006-8993(82)90837-x. [DOI] [PubMed] [Google Scholar]
  27. Wuttke W. A. Mechanism of potassium uptake in neuropile glial cells in the central nervous system of the leech. J Neurophysiol. 1990 May;63(5):1089–1097. doi: 10.1152/jn.1990.63.5.1089. [DOI] [PubMed] [Google Scholar]
  28. la Cour M. Kinetic properties and Na+ dependence of rheogenic Na(+)-HCO3- co-transport in frog retinal pigment epithelium. J Physiol. 1991 Aug;439:59–72. doi: 10.1113/jphysiol.1991.sp018656. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from The Journal of Physiology are provided here courtesy of The Physiological Society

RESOURCES