Maximal stimulation of pancreatic islet B-cells, and A-cell response to arginine, in dogs with longterm pancreatic acinar atrophy

Abstract

The response of the pancreatic islet A- and B-cells after long-standing (eight years) pancreatic duct occlusion by prolamine, and subsequently developed acinar atrophy, was studied in five beagles, and the results compared with those in six sham-operated dogs. Intravenous arginine infusion (A-cell stimulation) and a combined oral glucose and intravenous tolbutamide and glucagon infusion (B-cell stimulation) were carried out in each dog. Complete abolition of acinar function after duct occlusion was documented by the negative paraaminobenzoic acid test. In contrast, in plasma, baseline values of glucose, alpha-amino-nitrogen, insulin, glucagon, glucagon-like immunoreactivity, somatostatin-like immunoreactivity, and pancreatic polypeptide did not differ between the experimental groups. During B-cell stimulation dogs with occluded ducts had significantly reduced insulin, reduced glucagon, and reduced second phase pancreatic polypeptide compared with controls. Integrated insulin and pancreatic polypeptide were also reduced in dogs with occluded ducts. In both groups plasma and integrated values of glucose and somatostatin-like immunoreactivity did not differ. During the A-cell stimulation period dogs with occluded ducts had significantly raised alpha-amino-nitrogen but unchanged glucose and reduced insulin concentrations; in both groups the arginine-induced rise in glucagon was similar, although it was delayed in the experimental group. In the latter, integrated alpha-amino-nitrogen was raised, but integrated glucose and hormones were unchanged. We conclude that a previously intact dog pancreas that has been atrophied by duct occlusion, may be able to maintain euglycaemia for several years. There may be a complex interplay of changes induced by duct occlusion at the level of the pancreatic islets and elsewhere, which compensate for moderate insulinopenia.