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First published online October 21, 2004
Journal of Experimental Biology 207, 4077-4084 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01254

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Calcium handling in Sparus auratus: effects of water and dietary calcium levels on mineral composition, cortisol and PTHrP levels

Wout Abbink¹, Gideon S. Bevelander¹, Josep Rotllant², Adelino V. M. Canario² and Gert Flik^1,*

¹ Department of Animal Physiology, Faculty of Science, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
² Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal

View larger version (20K): [in a new window]   Fig. 1. Growth during the nine-weeks exposure to calcium-limited conditions. In the group exposed to limited calcium in both external calcium sources, diet and medium, growth arrest occurs. Values are means ± S.D. Asterisks represent significant difference from control group (P<0.05).

View larger version (12K): [in a new window]   Fig. 2. (A) Net calcium and phosphorus accumulation (µmol h-1) during three weeks under calcium-limited conditions and (B) the relationship between net calcium and net phosphorus accumulation (R2=0.92, N=16, P<0.01). Values are means ± S.D. Asterisks represent significant difference from control group (P<0.05).

View larger version (8K): [in a new window]   Fig. 3. The relationships between (A) wet mass and whole-body calcium content (R2=0.84, N=25, P<0.01) and (B) wet mass and whole-body phosphorus content (R2=0.88, N=24, P<0.01) for the control fish. For the test groups, similar correlations were found, although with lower regression slopes.

View larger version (15K): [in a new window]   Fig. 4. Total and ionic plasma calcium levels show the more strict correlation in ionic calcium compared with total calcium. Values are means ± S.D. Asterisks represent significant difference from control group (P=<0.05).

View larger version (12K): [in a new window]   Fig. 5. (A) Plasma cortisol is shown to increase at calcium-limiting conditions. (B) Parathyroid hormone related protein (PTHrP) increases when calcium is limited in the diet or the medium. However, when both external calcium sources are limited, PTHrP shows no rise in plasma level. Asterisks represent significant difference (P<0.05) compared with the control group. Values are means ± S.D.

View larger version (12K): [in a new window]   Fig. 6. A positive relationship between plasma parathyroid hormone related protein (PTHrP) and ionic calcium (R2=0.29, N=18, P<0.05) shows that PTHrP is involved in the strict control of plasma ionic calcium.