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Blood glucose was significantly decreased by insulin (4 I.U./kg). Glucagon (1 mg/kg) and Cortisol (5 mg/kg) administration produced a significant hyperglycaemia. Insulin administration did not modify liver glycogen levels. Glucagon showed a marked liver glycogen mobilization. Cortisol stimulated liver glycogen deposition. Insulin and Glucagon showed a significant inverse effect on gluconeogenesis from (U-14C)glutamate, decreasing and increasing 14C-glucose formation respectively. Hormonal treatments did not influence the very low levels of incorporation of (U-14C)glutamate into liver and muscle glycogen.

A partial hepatectomy (an average of 36% of hepatic mass removed) was performed in rainbow trout. Thirty days after this partial hepatic removal, the liver had recovered its initial weight. During regeneration the remaining liver was unable to maintain normal blood levels of protein, cholesterol and, partially, lipids which decrease after surgery. The results obtained show that functional and liver weight regeneration proceed at different rates throughout a given time course, weight recovering faster than complete functional restoration.

The nutritional and metabolic effects of the use of Hansenula anomala yeast as the only protein source were studied in the trout. Food intake, weight and length increments significantly decreased in trout fed on yeast diet. Hepatosomatic index did not suffer any change. Soluble protein content in liver and kidney rose significantly. Liver alkaline phosphatase activity increased significantly. Liver lactate dehydrogenase (LDH) activity did not change in the experimental conditions. Glutamic-oxalacetic transaminase (GOT) activity appeared as the most affected parameter in both organs, increasing significantly in those trout fed on yeast diet.

Nutritive utilization of protein was studied in three age weight rainbow trout (Salmo gairdnerii) groups fed on a 37.5% casein-protein diet. As to digestive efficiency age was found to have no influence on the apparent and true digestibility coefficient for protein. On the other hand Biological Value, Net Protein Utilization and Protein Productive Value decreased with age-weight increases, the results being significantly correlated (P less than 0.001) between these parameters and the age-weight of the animals. Relative intake, weight increment and Protein Efficiency Ratio also decreased with age-weight increases.

The effect of diets with different fatty acids composition on muscular and hepatic fatty acids of rainbow trout (Salmo gairdnerii) was studied. The effect was higher on muscular fatty acids than on hepatic ones. The lack of correlation between dietary and liver fatty acids in diets with a high level of linoleic acid, showed a better utilization of this acid by the liver. The change in muscular fatty acids pattern was observed within a week of diet change, showing a significant tendency to approach the new dietary fatty acids pattern.

After 36% of hepatic mass removal , rainbow trout recovered its initial liver weight in 20-30 days, i.e., with a regeneration rate clearly lower than in mammals. During early regeneration process hematocrit index and hemoglobin content were slightly decreased, but both parameters rapidly reached their normal values. The evolution of both glycaemia and hepatic glycogen content supported the idea of the existence of a late regeneration wave, which, in this case, could begin at about the 20th post-operative day.