GLUCOSE, LACTATE, AND BETA-HYDROXYBUTYRATE UTILIZATION BY RAINBOW-TROUT BRAIN - CHANGES DURING FOOD-DEPRIVATION

In order to evaluate the normal (fed conditions) substrate utilization rates of rainbow trout (Oncorhynchus mykiss) brain, CO2 production fr om glucose, lactate, and beta-hydroxybutyrate was tested in pooled bra ins. Oxidation rates, as well as the capacity for metabolism of carboh ydrate and ketone bodies, were also evaluated in brain of rainbow trou t that were food-deprived for 14 d. Under normal (fed) conditions, rai nbow trout brain oxidized glucose and lactate at rates higher than tho se described for mammals; oxidation rates of beta-hydroxybutyrate were lower in rainbow trout brain than those observed for lactate and gluc ose, and also lower than those described for mammals. Under food-depri vation conditions, glucose and lactate oxidation rates decreased in br ains, suggesting the existence of brain metabolic depression, and beta -hydroxybutyrate oxidation rates sharply increased, suggesting increas ed utilization of ketone bodies.