Differential effects of chronic ethanol exposure on ATP- and bradykinin-induced increases in intracellular calcium levels in PC-12 cells.
The present study investigated the regulation of intracellular calcium levels ([Ca2+]i) by ethanol, ATP, and bradykinin (BK) in PC-12 cells. Acute addition of 150 mM ethanol increased [Ca2+]i but did not alter ATP- and BK-induced increases in [Ca2+]i. After a 4-day exposure to 150 mM ethanol, the maximal response to ATP was decreased 39.7 +/- 8.12% (p < 0.01), whereas that to BK was increased 43.8 +/- 6.81% (p < 0.01). There was no change in the EC50 values for either ATP or BK after chronic ethanol exposure. Addition of excess ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) to remove extracellular free calcium prevented the ATP-induced increase in [Ca2+]i. In contrast, BK produced an increase in [Ca2+]i in the presence of excess EGTA, suggesting that BK releases calcium from internal stores. Consistent with this suggestion, chronic ethanol exposure enhanced BK-induced phosphoinositide hydrolysis. ATP, however, did not increase phosphoinositide hydrolysis. Pretreatment with 10 microM nifedipine, which blocked depolarization-evoked increases in [Ca2+]i, reduced ATP- and BK-induced increases in [Ca2+]i but did not alter the response to chronic ethanol exposure. Although acute addition of ethanol reduced KCl-stimulated increases in [Ca2+]i and 45Ca2+ uptake, chronic ethanol exposure did not alter the depolarization-induced increase in [Ca2+]i or 45Ca2+ uptake. The present study demonstrates that chronic ethanol exposure inhibits calcium influx through voltage-independent cationic channels associated with purinergic receptors and enhances BK-stimulated phosphoinositide hydrolysis, with a subsequent release of calcium from internal stores.
Kim
W K
WK
Department of Pharmacology, State University of New York, Buffalo 14214-3000.
Hawthorn
M
M
Rabin
R A
RA
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001665:Binding Sites; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D004533:Egtazic Acid / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D006868:Hydrolysis; D007295:Inositol Phosphates / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D016716:PC12 Cells; D013050:Spectrometry, Fluorescence
D015220:Calcium Channels; D007295:Inositol Phosphates; D000431:Ethanol; D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D009543:Nifedipine; D001920:Bradykinin; D002118:Calcium