Influence of salinity and food deprivation on growth, RNA/DNA ratio and certain enzyme activities in rainbow trout ( Salmo gairdneri Richardson)

Abstract

1. 1. Rainbow trout held in freshwater and diluted sea-water (8%, 20%) were starved or fed. 2. 2. Weight loss and mortality caused by starvation were lowest among the rainbow trout held at a salinity of 8%. 3. 3. The rainbow trout held at a salinity of 20% grew more slowly during our experiments than those held in freshwater and at 8% S. 4. 4. Starvation leads to a reduction in the liver RNA/DNA ratio. 5. 5. Starvation reduces gill Na/K-ATPase activity in trout held in freshwater and prevents it from increasing in trouts held in diluted sea-water. 6. 6. Specific changes were also observed in the activities of other enzymes investigated in the liver (glutamate dehydrogenase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, isocitrate dehydrogenase, aspartate aminotransferase), kidney (glutamate dehydrogenase, aspartate aminotransferase), white muscle (alanine aminotransferase, aspartate aminotransferase) and red muscle (aspartate aminotransferase and glutamate dehydrogenase).