Intestinal absorption of glycine, l-alanine and l-leucine in the old rat

Abstract

By use of the modified Sheff and Smyth method for studying neutral amino acid absorption in vivo, it is demonstrated that the intestinal of l-leucine in the (>24-month-old) rat is similar to that of the young (6-month-old) animal. The glycine absorption in the young resembles the absorption rates found in the old. The results with l-alanine show that the lowest intestinal affinity was observed in the old group. Relatively large scatters appeared mainly amongst the aged animals which might be accounted for by the diverticuloses found frequently in the old rat. The adults revealed a higher intestinal affinity with glycine and alanine, whilst the leucine data show that the maximal rate of release (apparent maximal rate of velocity) occurs in the group of 12-month-old animals. Almost all these figures were confirmed by analyzing the ratios of radiocarbon activity incorporated of liver to intestine of the various age-groups. The data obtained suggest that, there is no reason to suppose that a clear-cut difference exists in the intestinal absorption of the amino acids tested between the young and old rat.