| Abstrakt: |
Drinking in Atlantic salmon ( Salmo salar) juveniles was investigated in fresh water and following transfer to sea water. There was a significant effect of fish size on drinking, and smolts (20–30 g) imbibed about ten times less water than alevins of 0.2–0.3 g. Freshwater smolts drank at a rate of 0.15 ± 0.03 ml · kg−1 · h−1 and administration of doses of 10 or 20 mg · kg−1 of papaverine (stimulator of the renin- angiotensin system RAS) or [Asn1, Val5]-Angiotensin II (0.4 μmol · kg−1) resulted in significant increases in drinking, while administration of the angiotensin converting enzyme inhibitor, enalapril (50 mg · kg−1) had no effect on drinking. Transfer of Atlantic salmon smolts to 1/3, 2/3 and full strength sea water resulted in significant increases in drinking to 1.06 ± 0.12, 1.24 ± 0.0.16 and 3.89 ± 0.28 ml · kg−1 · h−1, respectively. In sea water, stimulation of the endogenous RAS by administration of papaverine (20 mg · kg−1) resulted in a 20% increase in drinking, while administration of enalapril to doses of 50 and 200 mg · kg−1 lowered drinking to 1.99 ± 0.48 and 0.32 ± 0.06 ml · kg−1 · h−1, respectively. All treatments were without effect on blood plasma levels of Na+ and Cl− in fresh water, while in sea water smolts both stimulation and inhibition of drinking resulted in hemoconcentration of Na+ and Cl−. The role of the renin angiotensin system in control of drinking and hydromineral balance in Atlantic salmon is discussed. [ABSTRACT FROM AUTHOR] |
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