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Title: A Toxin Fraction (FTX) from the Funnel-Web Spider Poison Inhibits Dihydropyridine-Insensitive Ca2+ Channels Coupled to Catecholamine Release in Bovine Adrenal Chromaffin Cells
Authors: Duarte, Carlos B. 
Rosário, Luís M. 
Sena, Cristina M. 
Carvalho, Arsélio P. 
Issue Date: 1993
Citation: Journal of Neurochemistry. 60:3 (1993) 908-913
Abstract: In adrenal chromaffin cells, depolarization-evoked Ca2+ influx and catecholamine release are partially blocked by blockers of L-type voltage-sensitive Ca2+ channels. We have now evaluated the sensitivity of the dihydropyridine-resistant components of Ca2+ influx and catecholamine release to a toxin fraction (FTX) from the funnel-web spider poison, which is known to block P-type channels in mammalian neurons. FTX (1:4,000 dilution, with respect to the original fraction) inhibited K+-depolarization-induced Ca2+ influx by 50%, as monitored with fura-2, whereas nitrendipine (0.120131 03BCM) and FTX (3:3), a synthetic FTX analogue (1 mM), blocked the [Ca2+]i transients by 35 and 30%, respectively. When tested together, FTX and nitrendipine reduced the [Ca2+]i transients by 70%. FTX or nitrendipine reduced adrenaline and noradrenaline release by 223C80 and 70%, respectively, but both substances together abolished the K+-evoked catecholamine release, as measured by HPLC. The 03C9-conotoxin GVIA (0.5 03BCM) was without effect on K+-stimulated 45Ca2+ uptake. Our results indicate that FTX blocks dihydropyridine- and 03C9-conotoxin-insensitive Ca2+ channels that, together with L-type voltage-sensitive Ca2+ channels, are coupled to catecholamine release.
DOI: 10.1111/j.1471-4159.1993.tb03236.x
Rights: openAccess
Appears in Collections:FCTUC Ciências da Vida - Artigos em Revistas Internacionais

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