Comparison of D- and L-phenylalanine as pancreatic stimulants.

MEYER, JAMES H., AND MORTON I. GROSSMAN. Comparison of Dand L-phenylalanine as pancreatic stimulants. Am. J. Physid. 222(a) : 1058-1063. 1972.-In dogs with pancreatic fistulas and arrangements for perfusing intact intestine, the following observations were made: 1) during continuous intravenous infusion of a submaximal dose of secretin, instillation of L-phenylalanine at pH 7 into the duodenum increased pancreatic volume and bicarbonate and protein output, but at pH 7 D-phenylalanine had no effect; 2) perfusion of the proximal 45 cm of small intestine with L-phenylalanine at pH’s varying from 1.3 to 7.5 produced significantly larger pancreatic protein outputs than D-phenylalanine at each pH; 3) intraduodenal infusion of 1, 2, 3, or 4 mEq/l5 min of HCl alone or these same amounts of HCl with 3.2 mmoles of Dor L-phenylalanine added showed that pancreatic bicarbonate and protein responses to HCl alone and HCl plus D-phenylalanine were not significantly different, whereas both bicarbonate and protein responses were larger with HCl plus L-phenylalanine than with HCl alone. Conclusions drawn are a) intraduodenal L-phenylalanine stimulates pancreatic secretion, whereas n-phenylalanine does not; b) stimulation by L-phenylalanine is not abolished by acidification to pH 1.3; and c) the stimulus of intraduodenal L-phenylalanine interacts with the stimulus of intraduodenal acid to produce a potentiated response.