title: Effect of temperature on the uptake of waterborne strontium in the common carp, Cyprinus carpio (L.).
abstract: The effect of temperature on the uptake kinetics of strontium (Sr) in the common carp (Cyprinus carpio) was studied in vivo, exposing pre-acclimated fish to a wide range of Sr concentrations in water (Sr(total)=0.2-10,000 microM; Ca(total)=348 microM) at 10, 20, 25 and 30 degrees C. Sr uptake rates were determined in the whole body, gills and blood of the fish after an exposure period of 3 h and were analyzed as a function of the free-ion activity of Sr and Ca in water. The uptake of Sr(2+) by the whole body, gills and blood increased with temperature and showed saturation kinetics with the increase of Sr(2+) activity. Analyzing the observed uptake rates with a Michaelis-Menten type model showed that the kinetic parameters (J(max), K(m) and K(i)) for both Sr(2+) and its analogue Ca(2+) are temperature dependent. Thermodynamic analysis of the temperature effects indicates that the Arrhenius activation energies (E(a)) required for Sr(2+) uptake (91.9 kJ mol(-1)) and Ca(2+) uptake (105.9 kJ mol(-1)) in the whole body of carp were constant over the temperature range 10-25 degrees C and showed a break in the Arrhenius plots above this temperature. The Arrhenius plot for the Sr(2+) uptake in blood was similar to that for the whole body uptake with an E(a) of 98.1 kJ mol(-1). However, the E(a) for Sr(2+) uptake in gills was much smaller and constant (58.1 kJ mol(-1)) over the temperature range of 10-30 degrees C. For a temperature change from 10 to 25 degrees C, the Q(10) for Sr(2+) uptake in whole fish, gills and blood were 3.71, 2.29 and 4.05, respectively. Compared with Ca(2+) uptake, Sr(2+) uptake appears to require a lower activation energy for transport across the solution body interface in carp. The similar pattern of Arrhenius plots and magnitude of activation energies for Sr(2+) uptake both in blood and whole fish suggest that the uptake into the blood across the basolateral membrane is the rate-limiting energy barrier and hence dictates the overall uptake rate of Sr(2+) in whole fish.
authors.affiliation: Department of Biology, University of Antwerp (RUCA), Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: M J
authors.initials: MJ
authors.lastname: Chowdhury
authors.forename: R
authors.initials: R
authors.lastname: Blust
mesh_terms: D000818:Animals; D002118:Calcium / Q000737:chemistry; D002347:Carps / Q000502:physiology*; D005880:Gills / Q000502:physiology; D007700:Kinetics; D013324:Strontium / Q000493:pharmacokinetics*; D013326:Strontium Radioisotopes / Q000493:pharmacokinetics*; D013696:Temperature; D014873:Water Pollutants / Q000493:pharmacokinetics*
chemical_list: D013326:Strontium Radioisotopes; D014873:Water Pollutants; D002118:Calcium; D013324:Strontium