DEVELOPMENTAL-CHANGES AND DIETARY HISTIDINE MANIPULATION - EFFECT ON RAT OLFACTORY-BULB AND LEG MUSCLE COMPONENTS

Rat olfactory bulb constituents, including carnosine, freehistidine and γ-aminobutyric acid (GABA) were studied as a function of age (19-day fetus to 7 weeks postpartum) and as a function of dietary histidine intake (100% growth requirement versus 75% of requirement). Carnosine was not detected in the 19-day fetal olfactory lobes but was found 3 days after birth and continued to increase in concentration thereafter. After 4 weeks of reduced histidine intakes (75% of requirement), carnosine dropped to one-third the starting level. This was a much sharper decrease than was observed by us in older rats (1977). Free histidine was relatively high in fetal olfactory bulbs and decreased with age in a manner similar to the increase observed in carnosine concentration as a function of age. Anserine, carnosine and histamine concentrations in leg muscle of 5-week old rats were also studied as a function of dietary histidine level (100% growth requirement versus 50% of requirement). Anserine concentration was not affected by dietary histidine level, whereas carnosine decreased about 50% after only 2 weeks on the lower histidine intake. Histamine concentration increased with reduced histidine intake in comparison with the control (100% requirement) diet. Hemoglobin levels were not affected, as they were in older rats in the earlier study cited above. Age, therefore, affects the priority for histidine as utilized in histidine-containing or derived compounds.