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First published online January 27, 2004
Journal of Experimental Biology 207, 813-825 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00826

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Characterization of branchial lead-calcium interaction in the freshwater rainbow trout Oncorhynchus mykiss

Joseph T. Rogers^* and Chris M. Wood

Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada

View larger version (12K): [in a new window]   Fig. 1. (A) Calcium influx rates in juvenile rainbow trout in City of Hamilton dechlorinated tapwater in control conditions (black bars) or water containing 2.3±0.1 µmol l-1 dissolved lead (white bars) after exposure for 0, 12 or 24 h. (B) Calcium influx rates in control water (black bars) or water containing 1.4±0.2 µmol l-1 dissolved lead (white bars) after exposure for 0, 12 or 24 h. Values are means ± 1 S.E.M. (N=8 throughout). *Significant difference (P<0.05; two-tailed Student's t-test) from corresponding control means.

View larger version (18K): [in a new window]   Fig. 2. Unidirectional branchial calcium influx rates in juvenile rainbow trout at various waterborne calcium concentrations in synthetic water for four different lead concentrations. Control fish, black circles; fish exposed to 0.46±0.03 µmol l-1 dissolved lead, white triangles; 2.5±0.2 µmol l-1 lead, white circles; 4.9±0.3 µmol l-1 lead, white squares. Values are means ± 1 S.E.M. (N=7 per treatment).

View larger version (12K): [in a new window]   Fig. 3. Analytical plots for data presented in Fig. 2 using (A) Michaelis-Menten analyses by Lineweaver-Burk regression (double reciprocal plot) illustrating the competitive relationship between lead and calcium uptake in the rainbow trout, and (B) regression analyses of apparent Km/Jmax vs. waterborne lead concentration (using apparent Km and Jmax values presented in Table 1. The regression equation was y=2.38x+1.12 (r2=0.95). The inhibitor constant (-Ki,Pb, the x-intercept of the regression line) was 0.48 µmol l-1 lead.

View larger version (17K): [in a new window]   Fig. 4. Measurements of branchial lead accumulation in juvenile rainbow trout at various waterborne calcium concentrations in synthetic water for four different lead concentrations. Values are means ± 1 S.E.M. (N=7 per treatment). *Significant difference (P<0.05; two-tailed Student's t-test) from corresponding lead uptake in the presence of 1300 µmol l-1 calcium.

View larger version (20K): [in a new window]   Fig. 5. (A) Percentage inhibition of calcium uptake in juvenile rainbow trout exposed to control conditions (black bar) or 1 µmol l-1 lanthanum, 1 µmol l-1 cadmium or 100 µmol l-1 zinc (white bars) in synthetically modified water (600 µmol l-1 Ca2+). (B-D) Branchial lead accumulation in juvenile rainbow trout exposed to control conditions (black circles) or (B) a series of waterborne lanthanum concentrations, (C) a series of waterborne cadmium concentrations, and (D) a series of waterborne zinc concentrations. Values are means ± 1 S.E.M. (N=7 per treatment). *Significant difference (P<0.05; two-tailed Student's t-test) from corresponding control mean.

View larger version (12K): [in a new window]   Fig. 6. (A) The effects of the voltage-dependent Ca2+ channel blockers nifedipine and verapamil on calcium uptake in juvenile rainbow trout exposed to control conditions (black bars) or 100 µmol l-1 nifedipine and 100 µmol l-1 verapamil (white bars) in synthetically modified water (600 µmol l-1 Ca2+). (B,C) The effect of nifedipine on branchial lead accumulation in juvenile trout exposed to control conditions (black circle) or (B) to 0.1, 1, 10 and 100 µmol l-1 nifedipine (white circles), (C) to 0.1, 1, 10 and 100 µmol l-1 verapamil (white circles). Values are means ± 1 S.E.M. (N=7 per treatment).

View larger version (15K): [in a new window]   Fig. 7. The effect of CaCl2 injection on (A) Ca2+ influx in juvenile rainbow trout in synthetically modified water (600 µmol l-1 Ca2+), and (B) branchial lead accumulation in juvenile rainbow trout. Values are means ± 1 S.E.M. (N=7 per treatment). *Significant difference (P<0.05; two-tailed Student's t-test) from corresponding control mean.

View larger version (15K): [in a new window]   Fig. 8. Time course analysis of (A) branchial high affinity Ca2+-ATPase activity in adult rainbow trout, and (B) branchial lead accumulation, and (C) plot of high-affinity Ca2+-ATPase activity versus branchial lead accumulation in rainbow trout exposed to control conditions and to 5.5±0.4 µmol l-1 dissolved lead for 3 h, 24 h and 96 h. Values are means ± 1 S.E.M. (N=6). *Significant difference (P<0.05; one-way ANOVA with Dunnett's post-hoc multiple comparison) from control sampling mean.