title: Ca2+ uptake and Cd2+ accumulation in larval tilapia (Oreochromis mossambicus) acclimated to waterborne Cd2+.
abstract: The present study compares the rates of Ca2+ uptake and Cd2+ accumulation in tilapia (Oreochromis mossambicus) between larvae preexposed to Cd2+ and naive larvae. Preexposure to Cd2+ induces some form of adaptation that attenuates the effects of Cd2+ later on. Exposure to Cd2+ decreased the uptake of Ca2+ but did not suppress the accumulation rate of Cd2+. A 12-fold increase in 96-h half-maximal lethal concentration was found in tilapia larvae preexposed to 0.45 microM Cd2+ from hatching for 3 days in comparison with naive 3-day-old larvae. The effects of Cd2+ on Ca2+ influx kinetics in larvae preexposed to 0.18 microM Cd2+ for 3 days were examined. The Michaelis constant for Ca2+ in the 0.18 microM Cd2+ preexposed larvae did not change significantly in the presence of Cd2+, whereas maximal velocity increased by approximately 23%. An enhanced Ca2+ uptake efficiency ( approximately 18%) was found in these Cd2+-acclimated larvae. The criterion that determines the survival of tilapia larvae encountering Cd2+ challenge is the degree of interference with Ca2+ homeostasis instead of the absolute amount of Cd2+ accumulated.
authors.affiliation: Department of Biology, Tunghai University, Taichung 407, Republic of China.
authors.forename: M H
authors.initials: MH
authors.lastname: Chang
authors.forename: H C
authors.initials: HC
authors.lastname: Lin
authors.forename: P P
authors.initials: PP
authors.lastname: Hwang
mesh_terms: D000064:Acclimatization; D000818:Animals; D002104:Cadmium / Q000378:metabolism* / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D007700:Kinetics; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D007928:Lethal Dose 50; D012996:Solutions; D017210:Tilapia / Q000254:growth & development / Q000378:metabolism*
chemical_list: D012996:Solutions; D002104:Cadmium; D002118:Calcium