Changes in sodium,calcium and magnesium ion concentrations in sturgeon (Huso huso) urine and in kidney morphology |
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Authors: | L S Krayushkina A A Panov A A Gerasimov W T W Potts |
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Institution: | (1) Department of Ichthyology and Hydrobiology, St Petersburg State University, 16 line, 29, 199178 St Petersburg, Russia;(2) Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Science, Torez Avenue 44, 194223 St Petersburg, Russia;(3) Biological Sciences, University of Lancaster, LA1 4QR Lancaster, UK |
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Abstract: | During adaptation to brackish water the young great sturgeon Huso huso is able to regulate its serum osmolarity and ion concentrations. After transfer from fresh water to brackish water the ion concentrations in the urine increase and the urine becomes isoosmotic to the blood serum after 24h. The Na+ and K+ concentrations in the urine increase during the first 12 h by 4.4 and 7.7 times, respectively, later decreasing again. The Mg2+ and Ca2+ concentrations in the urine increase by 3.4 and 14 times during the first 72h in brackish water and remain high thereafter. These results suggest that the kidneys play an important part in the regulation of serum osmolarity and in the removal of Ca2+; however, in contrast to teleosts, Mg2+ must be removed extrarenally. During adaptation to a hyperosmotic medium the diameters of the Malpighian bodies, the glomeruli and the diameter of the tubules initially all decrease, but the distal tubules become morphologically differentiated into two regions and the diameter of the distal section later increases again. It is suggested that this is the site of Ca2+ secretion into the urine. |
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Keywords: | Sturgeon Kidney Urine Magnesium Calcium Huso huso |
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