UPTAKE OF TRYPTOPHAN INTO BRAIN OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Brain and plasma levels of tryptophan, 30 min after intraperitoneal ad ministration of increased doses of L-tryptophan (0, 12.5, 25, 37.5, 50 , 62.5, 75, 87.5, 100, 150, and 200 mg/kg body wt), D-tryptophan (0, 2 5, 50, 75, 150 mg/kg body wt) or the joint administration of L-tryptop han and L-tyrosine (75 mg/kg body wt), were analyzed spectrofluorimetr ically. The results show that the uptake of tryptophan into the brain takes place through a stereospecific and saturable carrier, which is c ommon for tyrosine and possibly other neutral aminoacids, in a way sim ilar to that observed for mammals. On the other hand, the findings ind icate that the uptake of tryptophan into brain of rainbow trout seems to be little sensitive to the effects of competition with other amino acids. (C) 1998 Wiley-Liss, Inc.