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Hernandez-Cruz, A; Ardon, F; Rodriguez-Miranda, E; Beltran, C; Darszon, A (2009)

MITOCHONDRIAL INHIBITORS ACTIVATE INFLUX OF EXTERNAL CA2+ IN SEA URCHIN SPERM

BBA-BIOENERGETICS 1787(1):15-24
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Sea urchin sperm have a single mitochondrion which, aside from its main ATP generating function, may regulate motility, intracellular Ca2+ concentration ([Ca2+](i)) and possibly the acrosome reaction (AR). We have found that acute application of agents that inhibit mitochondrial function via differing mechanisms (CCCP, a proton gradient uncoupler, antimycin, a respiratory chain inhibitor, oligomycin, a mitochondrial ATPase inhibitor and CGP37157, a Na+/Ca2+ exchange inhibitor) increases [Ca2+](i) with at least two differing profiles. These increases depend on the presence of extracellular Ca2+, which indicates they involve Ca2+ uptake and not only mitochondrial Ca2+ release. The plasma membrane permeation pathways activated by the mitochondrial inhibitors are permeable to Mn2+. Store-operated Ca2+ channel (SOC) blockers (Ni2+, SKF96365 and Gd2+) and internal-store ATPase inhibitors (thapsigargin and bisphenol) antagonize Ca2+ influx induced by the mitochondrion regulates Ca2+ entry through SOCs. As neither CCCP nor dicycloexyl carbodiimide (DCCD) another mitochondrial ATPase inhibitor, eliminate the oligomycin induced increase in [Ca2+](i), apparently oligomycin also has an extra mitochondrial target. (C) 2008 Elsevier B.V. All rights reserved.