title: Copper transport by lobster (Homarus americanus) hepatopancreatic mitochondria.
abstract: Mechanisms of copper transport into purified mitochondrial suspensions prepared from the hepatopancreas of the Atlantic lobster Homarus americanus were investigated. Mitochondria were purified by combining methods of differential and Percoll-gradient centrifugation, and copper transport was studied using the copper-sensitive fluorescent dye Phen Green. Copper transport by this mitochondrial preparation was kinetically the sum of saturable and non-saturable transfer components. Addition of 500 micromol x l(-1) Ca2+ or 500 nmol x l(-1) Ruthenium Red abolished the non-saturable copper transport component, significantly (P<0.01) reduced the apparent binding affinity of the saturable transport component, but was without effect (P>0.05) on the apparent maximal transport velocity of the saturable transfer process. The antiport inhibitor diltiazem (500 micromol x l(-1)) acted as a mixed inhibitor of the saturable transport mechanism, but had no effect on the non-saturable component of transfer. These results suggest that the non-saturable copper influx process was probably by way of the well-known Ruthenium-Red-sensitive Ca2+ uniporter and that the saturable transport component was probably due to a combination of both the Na+-dependent, diltiazem-sensitive 1Ca2+/2Na+ antiporter and the Na+-independent, diltiazem-insensitive 1Ca2+/2H+ antiporter. A model is discussed relating these mitochondrial copper uptake processes to the transfer of metal ions across the epithelial brush-border membrane.
authors.affiliation: Department of Zoology, 2538 The Mall, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
authors.forename: Pamela
authors.initials: P
authors.lastname: Chavez-Crooker
authors.forename: Nestor
authors.initials: N
authors.lastname: Garrido
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Ahearn
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003300:Copper / Q000378:metabolism*; D004064:Digestive System / Q000648:ultrastructure*; D004110:Diltiazem / Q000494:pharmacology; D005456:Fluorescent Dyes; D007700:Kinetics; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D008121:Nephropidae / Q000378:metabolism*; D009930:Organic Chemicals; D012430:Ruthenium Red / Q000494:pharmacology
chemical_list: D005456:Fluorescent Dyes; D009930:Organic Chemicals; C431805:Phen Green SK; D012430:Ruthenium Red; D003300:Copper; D004110:Diltiazem