Abstract
Plasma phenylalanine and tyrosine levels in rats which had been orally administered L-phenylalaninol and L-phenylalanine were determined. Since these amino acid levels in rats administered L-phenylalanine solution containing L-phenylalaninol were significantly lower than those in rats administered L-phenylalanine alone, L-phenyl-alaninol appears to inhibit the intestinal absorption of L-phenylalanine. This effect was more potent than that of cycloleucine.
L-Phenylalaninol inhibited the phenylalanine transport of everted sacs. The Km value of L-phenylalanine was 3.44×10-3M and the Ki value of L-phenylalaninol was 7.69×lO-3M from Lineweaver-Burk plots. From these two curves, it appeared that L-phenylalaninol may competitively inhibit the intestinal transport of L-phenylalanine.
The effects of L-phenylalanine, L-phenylalaninol and cycloleucine on the urinary excretions of Na+ and K+ in rats were also examined. Potassium excretion, which increased on oral administration of L-phenylalanine, was suppressed by the administration of L-phenylalaninol but not by administration of cycloleucine. L-Phenyl-alaninol alone enhanced Na+ excretion in urine.
These results confirmed that L-phenylalaninol shows inhibitory effects as potent as those of cycloleucine on the intestinal absorption of L-phenylalanine.
