Possible Interaction: Phenylalanine and Triiodothyronine

“Proliferation assays using HCT-116 cells showed that addition of inhibitors phenylalanine and T3 both increased cell proliferation, whereas addition of the activator F16BP reduced proliferation.”

“The aromatic amino acids phenylalanine and tryptophan were found to inhibit the uptake of T3 , but these two amino acids were transported into the cells predominantly via system L. The amino acid transport system T, which is specific for aromatic amino acids, was not detectable in these cells.”

“Urinary excretion of 3‐methylhistidine and plasma concentrations of valine, methionine, lysine, tyrosine, phenylalanine , isoleucine, leucine, and total essential and branched chain amino acids increased following administration of T3 , probably in part reflecting accelerated muscle proteolysis.”

“Moreover, the concentrations of Leu, Phe , and Arg were higher in T2 and T3 (P < 0.05).”

“ Phenylalanine and tyrosine (but not the D-isomer of tryptophan or non-aromatic amino acids) also produced trans-acceleration for T3 uptake and T3 countertransport.”

“Furthermore, L-system neutral amino acids, in particular L-phenylalanine at physiological concentrations, were shown to be competitive inhibitors of both T3 and T4 transport.”

“In the presence of 0.1 mM L-phenylalanine the Km of the saturable plasma membrane transport of L-T3 increased 2.3-fold, and that of L-T4 increased 2.1-fold.”

“ Phenylalanine release was decreased by 26 +/- 2.3% (P less than 0.001) by the optimal concentrations of T3 (10(-7) to 10(-6) M).”

“Tyrosine concentrations did not significantly differ between the different time points, but phenylalanine concentrations were significantly lower at T2 and T3 compared to T1 (50.1 μmol/L, 29.8 μmol/L, and 37.3 μmol/L, respectively).”

“Vice versa, uptake of 0.1 M T3 was almost completely blocked by coincubation with 100 M leucine, tryptophan, tyrosine, or phenylalanine.”