Abstract
Effects of protein deprivation and excessive administration of L-histidine on the accumulation of L-histidine in rat small intestine in vitro were investigated using tissue strips and rings. Compared with a 20% casein diet, a non-protein diet and a 5% casein + 5% L-histidine diet significantly enhanced the accumulation of L-histidine per unit wet weight of the tissue strips. The amount of endogenous L-histidine in the intestine of the animals fed on the excess L-histidine diet was extremely larger than that of animals fed on 20% casein and non-protein diets. Net accumulation per unit wet weight of the strips, calculated by taking into account the endogenous levels of L-histidine, was still significantly higher for rats fed on non-protein and excess L-histidine diets. However, the accumulations expressed in terms of the whole animal were identical irrespective of the dietary regimens. Also, with the intestinal rings no such significant difference as with the intestinal strips was observed among rats with different dietary regimens. It is speculated that dietary conditions affect intestinal absorption by modifying intestinal thickness rather than by influencing the mucosal function to accumulate amino acid.
