Anomeric specificity of the insulin and glucagon secretory responses to D-glucose in lean and obese Zucker rats.

The perfused pancreas of lean and obese Zucker rats was exposed, in the presence of L-leucine, to the anomers of D-glucose, which were administered on four successive occasions in the alpha/beta/alpha/beta or beta/alpha/beta/alpha sequence. In 5 lean and 6 obese rats, alpha-D-glucose was more efficient than beta-D-glucose in both stimulating insulin secretion and suppressing glucagon release. Although D-glucose evoked a greater release of insulin and, during prolonged exposure to the hexose, a less pronounced suppression of glucagon secretion in obese than lean rats, the anomeric specificity of these secretory responses was not different in the two groups of animals. In one lean rat, however, alpha-D-glucose, while efficiently stimulating insulin release, failed on two occasions to inhibit glucagon secretion. This isolated observation raises the possibility that the anomeric specificity of functional events evoked by D-glucose in the endocrine pancreas may occasionally be perturbed.