Maćkowiak P.: Amino acid-induced insulin release from the perfused irat pancreas. The influence of phenylalanine and tyrosine. Acta physiol, pol. The effects of L or D phenylalanine and L tyrosine on insulin release from the perfused rat pancreas were investigated. It was found that in the presence of D-glucose, all three amino-acids stimulate insulin secretion. After L-Phe had been removed from perfusate in the presence or absence of L-Tyr, the secondary rise of insulin release (an “off response”) was noticed. This phenomenon did not follow to either D-Phe or L-Tyr.