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Octanol, a gap junction uncoupling agent, changes intracellular [H + ] in rat astrocytes
Author(s) -
Pappas Christopher A.,
Rioult Marika G.,
Ransom Bruce R.
Publication year - 1996
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/(sici)1098-1136(199601)16:1<7::aid-glia2>3.0.co;2-2
Subject(s) - cotransporter , intracellular ph , heptanol , biophysics , dids , amiloride , gap junction , intracellular , octanol , biochemistry , biology , chemistry , sodium , chromatography , membrane , organic chemistry , partition coefficient
Octanol rapidly closes gap junction channels but its mechanism of action is not known. Because intracellular [H + ], pH i , also affects the conductance of gap junctions, we studied octanol's effects on pH i in cultured rat astrocytes, which are highly coupled cells. Octanol (1 mM) caused an acid shift in the pH i of 90% of rat hippocampal astrocytes which averaged −0.19 ± 0.09 pH units in magnitude. In 58% of the cells tested, a biphasic change in pH i was seen; octanol produced an initial acidification lasting ∼10 min that was followed by a persistent alkalinization. The related gap junction uncoupling agent, heptanol, had similar effects on pH i . Octanol‐induced changes in pH i were similar in nominally HCO 3 − ‐free and HCO 3 − ‐containing solutions, although the rate of initial acidification was significantly greater in the presence of HCO 3 − . The initial acidification was inhibited in the presence of the stilbene DIDS, an inhibitor of Na + /HCO 3 − cotransport, indicating that octanol caused acidification by blocking this powerful acid extruder. The alkalinization was inhibited by amiloride which blocks the Na + /H + exchanger (NHE), an acid extruder, suggesting that the alkaline shift induced by octanol was caused by stimulation of NHE. As expected, octanol's effects on astrocytic pH i were prevented by removal of external Na + , which blocks both Na + /HCO 3 − cotransport and NHE. Octanol had only small effects on intracellular Ca 2+ (Ca 2+ i ) in astrocytes. Hepatocytes which, like astrocytes, are strongly coupled to one another, showed no change in pH i with octanol application. Fluorescence recovery after photobleaching (FRAP) was used to study the effect of changes in astrocyte pH i on degree of coupling in hippocampal astrocytes. Coupling was decreased by intracellular acid shifts ∼−0.2 pH units in size. Octanol's effects on astrocyte pH i were complex but a prompt initial acidification was nearly always seen and could contribute to the uncoupling action of this drug in astrocytes. Because octanol uncouples hepatocytes without changing their pH i , this compound clearly can influence gap junctional conductance independent of changes in pH i . © 1996 Wiley‐Liss, Inc.