Extra- and intracellular acid-base balance and ionic regulation in cod (Gadus morhua?) during combined and isolated exposures to hypercapnia and copper |
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Authors: | B K Larsen H-O Pörtner F B Jensen |
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Institution: | (1) Institute of Biology, Odense University, DK-5230 Odense M, Denmark, DK;(2) Alfred Wegener Institute for Polar and Marine Research, D-27568 Bremerhaven, Germany, DE |
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Abstract: | Cod (Gadus morhua) were exposed to hypercapnia (water Pco2 = 7.5 mmHg), elevated copper level (0.4 ppm) or a combination of both in order to study extra- and intracellular acid-base
regulation and the influence hereupon of copper. During pure hypercapnia, the extracellular respiratory acidosis was completely
compensated within 12 to 24 h via a chloride-mediated increase in extracellular HCO3
−]. Exposure to copper in normocapnic seawater caused a large and progressive increase in plasma Na+] and Cl−] and a metabolic acidosis. Exposure to copper in hypercapnic seawater was associated with smaller elevations of plasma Na+] and Cl−] than in normocapnic seawater, showing that hypercapnia had a protective effect on the copper-induced osmoregulatory disturbances.
The compensation of the hypercapnic acidosis was, however, slow and incomplete in fish exposed to both copper and hypercapnia.
Extracellular pH remained depressed by 0.3 pH units after 72 h. The data reveal that acid-base regulation was immediately
and persistently inhibited by copper. The limited acid-base regulation during combined copper and hypercapnia exposure was
chloride-mediated as during hypercapnia alone. Intracellular pH recovery was complete and very rapid in ventricular and skeletal
muscle tissues during environmental hypercapnia, whereas acid-base compensation in liver tissue was slower, the kinetics being
similar to that in the extracellular compartment. Intracellular pH compensation was significantly slowed down by copper. Copper
concentration increased drastically in gill tissue already at 3 h, while copper concentrations in liver, muscle and plasma
were significantly elevated only after 48 h, with liver showing the largest elevation.
Received: 15 November 1996 / Accepted: 2 December 1996 |
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