title: Extracellular pH dynamics of retinal horizontal cells examined using electrochemical and fluorometric methods.
abstract: Extracellular H(+) has been hypothesized to mediate feedback inhibition from horizontal cells onto vertebrate photoreceptors. According to this hypothesis, depolarization of horizontal cells should induce extracellular acidification adjacent to the cell membrane. Experiments testing this hypothesis have produced conflicting results. Studies examining carp and goldfish horizontal cells loaded with the pH-sensitive dye 5-hexadecanoylaminofluorescein (HAF) reported an extracellular acidification on depolarization by glutamate or potassium. However, investigations using H(+)-selective microelectrodes report an extracellular alkalinization on depolarization of skate and catfish horizontal cells. These studies differed in the species and extracellular pH buffer used and the presence or absence of cobalt. We used both techniques to examine H(+) changes from isolated catfish horizontal cells under identical experimental conditions (1 mM HEPES, no cobalt). HAF fluorescence indicated an acidification response to high extracellular potassium or glutamate. However, a clear extracellular alkalinization was found using H(+)-selective microelectrodes under the same conditions. Confocal microscopy revealed that HAF was not localized exclusively to the extracellular surface, but rather was detected throughout the intracellular compartment. A high degree of colocalization between HAF and the mitochondrion-specific dye MitoTracker was observed. When HAF fluorescence was monitored from optical sections from the center of a cell, glutamate produced an intracellular acidification. These results are consistent with a model in which depolarization allows calcium influx, followed by activation of a Ca(2+)/H(+) plasma membrane ATPase. Our results suggest that HAF is reporting intracellular pH changes and that depolarization of horizontal cells induces an extracellular alkalinization, which may relieve H(+)-mediated inhibition of photoreceptor synaptic transmission.
authors.affiliation: Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Jacoby
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Kreitzer
authors.forename: Simon
authors.initials: S
authors.lastname: Alford
authors.forename: Haohua
authors.initials: H
authors.lastname: Qian
authors.forename: Boriana K
authors.initials: BK
authors.lastname: Tchernookova
authors.forename: Ethan R
authors.initials: ER
authors.lastname: Naylor
authors.forename: Robert Paul
authors.initials: RP
authors.lastname: Malchow
mesh_terms: D000468:Alkalies / Q000032:analysis / Q000378:metabolism; D000818:Animals; D002397:Catfishes; D002478:Cells, Cultured; D055664:Electrochemical Techniques; D005452:Fluoresceins / Q000032:analysis; D005470:Fluorometry / Q000379:methods*; D018698:Glutamic Acid / Q000494:pharmacology; D006054:Goldfish; D006863:Hydrogen-Ion Concentration; D018613:Microscopy, Confocal / Q000379:methods; D011188:Potassium / Q000494:pharmacology; D051248:Retinal Horizontal Cells / Q000378:metabolism*
chemical_list: D000468:Alkalies; D005452:Fluoresceins; D018698:Glutamic Acid; C058719:(hexadecanoyl)aminofluorescein; D011188:Potassium
references.citation: J Neurosci. 2008 May 28;28(22):5691-5
references.pmid: 18509030
references.citation: Neurosci Lett. 1984 Jun 1;47(1):1-7
references.pmid: 6462526
references.citation: Neurochem Res. 2005 Sep;30(9):1087-92
references.pmid: 16292500
references.citation: J Neurosci. 2008 Jan 9;28(2):456-64
references.pmid: 18184788
references.citation: J Gen Physiol. 1988 Apr;91(4):549-72
references.pmid: 2455767
references.citation: Pflugers Arch. 2001 Apr;442(1):142-9
references.pmid: 11374062
references.citation: J Neurophysiol. 2006 Mar;95(3):1992-5
references.pmid: 16371457
references.citation: J Neurochem. 2010 Oct;115(1):102-11
references.pmid: 20633206
references.citation: J Neurophysiol. 2010 Feb;103(2):667-76
references.pmid: 19939954
references.citation: Neuron. 1993 Aug;11(2):267-77
references.pmid: 8102533
references.citation: Ann N Y Acad Sci. 1997 Nov 3;834:407-9
references.pmid: 9405834
references.citation: J Gen Physiol. 2007 Aug;130(2):169-82
references.pmid: 17664345
references.citation: Handb Exp Pharmacol. 2008;(184):77-106
references.pmid: 18064412
references.citation: Neuron. 2001 Dec 20;32(6):1107-17
references.pmid: 11754841
references.citation: J Neurosci. 2011 Feb 2;31(5):1762-72
references.pmid: 21289186
references.citation: Proc Natl Acad Sci U S A. 1993 Nov 1;90(21):10081-5
references.pmid: 7694280
references.citation: Cell Mol Life Sci. 2011 Mar;68(5):903-17
references.pmid: 20820851
references.citation: Biochemistry. 1995 Jan 24;34(3):965-72
references.pmid: 7530047
references.citation: Brain Res. 1986 Sep 3;381(2):359-62
references.pmid: 3019478
references.citation: J Physiol. 1999 Feb 15;515 ( Pt 1):109-18
references.pmid: 9925882
references.citation: J Physiol. 1998 Jul 15;510 ( Pt 2):499-512
references.pmid: 9705999
references.citation: Am J Physiol Cell Physiol. 2001 Jan;280(1):C1-11
references.pmid: 11121371
references.citation: J Physiol. 1999 Jun 1;517 ( Pt 2):507-19
references.pmid: 10332098
references.citation: PLoS One. 2009 Jun 30;4(6):e6090
references.pmid: 19564917
references.citation: J Gen Physiol. 2003 Dec;122(6):657-71
references.pmid: 14610018
references.citation: J Neurosci. 1991 Dec;11(12):4015-23
references.pmid: 1660538
references.citation: J Neurosci. 1994 May;14(5 Pt 1):2648-58
references.pmid: 8182433
references.citation: J Biol Chem. 1998 Jul 17;273(29):18230-4
references.pmid: 9660785
references.citation: J Neurosci. 1992 Jun;12(6):2156-64
references.pmid: 1607934
references.citation: J Cell Biol. 1990 May;110(5):1565-73
references.pmid: 2335563
references.citation: J Biol Chem. 1994 May 13;269(19):14268-75
references.pmid: 8188711
references.citation: Microsc Res Tech. 1999 Sep 15;46(6):398-417
references.pmid: 10504217
references.citation: J Neurosci. 2005 Apr 20;25(16):4062-72
references.pmid: 15843608
references.citation: Am J Physiol. 1993 Jun;264(6 Pt 1):C1577-86
references.pmid: 7687411
references.citation: J Neurosci. 2005 Apr 20;25(16):4108-17
references.pmid: 15843613
references.citation: J Physiol. 2007 Dec 1;585(Pt 2):401-12
references.pmid: 17932147
references.citation: Ann N Y Acad Sci. 1991;635:468-70
references.pmid: 1660251
references.citation: J Cardiovasc Pharmacol. 1986;8 Suppl 8:S33-7
references.pmid: 2433522
references.citation: J Physiol. 2003 Jul 1;550(Pt 1):83-101
references.pmid: 12879862
references.citation: J Physiol. 2004 Nov 1;560(Pt 3):639-57
references.pmid: 15272044