title: Calcium efflux mechanism in sperm mitochondria.
abstract: This paper reports an investigation on calcium efflux mechanism in ram sperm mitochondria. Energized sperm mitochondria take up Ca2+ via the ruthenium-red sensitive uniporter, and possess a ruthenium-red insensitive efflux mechanism. Extramitochondrial Na+ did not affect the rate of Ca2+ efflux indicating that Na+/Ca2+ exchange mechanism is not involved. Depolarization of inner mitochondrial membrane induced by the uncoupler carbonylcyanide-p-trifluoromethoxyphenyl hydrazone (FCCP) or by the organomercurial SH-reagent mersalyl, causes high stimulation in Ca2+ efflux. This stimulated Ca2+ efflux determined in the presence of ruthenium-red and phosphate, is not inhibited by cyclosporin A (CSA), indicating that mitochondrial permeability transition pore (MTP) is not involved in this Ca2+ efflux mechanism. The stimulated Ca2+ efflux is inhibited by ADP or atractyloside suggesting that the Ca2+ transport mechanism might be intrinsic to the ADP/ATP carrier (AAC). Thus, the data indicate that sperm mitochondria contain a Ca2+ efflux mechanism operated via AAC and regulated by mitochondrial membrane potential and by ADP concentration.
authors.affiliation: Department of Life Sciences, Bar-Ilan University, Ramat Gan, Israel. breith@ashur.cc.biu.ac.il
authors.forename: H
authors.initials: H
authors.lastname: Breitbart
authors.forename: S
authors.initials: S
authors.lastname: Rubinstein
authors.forename: M
authors.initials: M
authors.lastname: Gruberger
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D001278:Atractyloside / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D004072:Digitonin / Q000494:pharmacology; D007773:Lactates / Q000494:pharmacology; D019344:Lactic Acid; D008297:Male; D008634:Mersalyl / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism; D010710:Phosphates / Q000494:pharmacology; D012430:Ruthenium Red / Q000494:pharmacology; D012756:Sheep; D013094:Spermatozoa / Q000378:metabolism*; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D007773:Lactates; D010710:Phosphates; D014475:Uncoupling Agents; C034703:mitochondrial calcium uniporter; D012430:Ruthenium Red; D001278:Atractyloside; D019344:Lactic Acid; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D008634:Mersalyl; D000244:Adenosine Diphosphate; D016572:Cyclosporine; D000226:Mitochondrial ADP, ATP Translocases; D004072:Digitonin; D002118:Calcium