Uptake of alanine, arginine and leucine by mammalian pancreatic beta-cells.

Abstract

Uptake of L-alanine, L-arginine, or L-leucine was studied in microdissected pancreatic islets of obese-hyperglycemic mice. These islets contain an unusually high proportion of the insulin-secreting (β-cells. The following main observations were made. 1. Alanine and arginine were concentrated by the islet cells to distribution ratios much higher than unity. This uptake was clearly saturable. Leucine did not accumulate to the same extent. 2. Islet uptake of alanine was much more dependent on sodium than was the uptake of leucine. Omission of calcium had little, if any, effect on the uptake of alanine and did not alter the uptake of leucine. 3. Methionine, but not leucine, inhibited the uptake of alanine. Isoleucine, but not D-leucine, inhibited the uptake of L-leucine. 4. The uptake of alanine was not stimulated by glucose, fructose, pyruvate, or succinate. Neither was the uptake of alanine, arginine, or leucine affected by diazoxide. 5. Glibenclamide, a potent hypoglycemic sulfonylurea, depressed the uptak...