CHANGES OF FREE AMINO ACIDS IN PANCREATIC β-CELLS AFTER STARVATION AND SUBSTRATE DEPRIVATION

Abstract

ABSTRACT A procedure for free amino acid measurements in β-cell-rich pancreatic islets from obese-hyperglycaemic mice involving reaction with 3H-dansyl chloride and subsequent chromatographic separation was studied. A characteristic feature of the islets was the presence of γ-aminobutyric acid and of very high taurine concentrations. Islets dissected from fresh pancreas contained more leucine and valine than specimens obtained from freeze-dried pancreatic sections. When micro-dissected islets were incubated in substrate-free medium the concentrations of leucine and valine remained high, whereas aspartic acid decreased. Perifusion of islets with the same type of medium, however, depressed the concentrations of glycine, leucine, lysine, phenylalanine and valine. Starvation increased the β-cell concentrations of γ-aminobutyric acid and leucine and reduced those of aspartic acid and glutamic acid. The possibilities that the amino acid concentrations are influenced by amino acid efflux or the uptake of secreted insulin in combination with protein catabolism are discussed.