Amylase activity was measured in homogenates of rat whole pancreas, is
olated islets and purified islet beta and non-beta islet cells. The sp
ecific activity of the enzyme, as expressed relative to protein conten
t, was 25 times higher in the pancreas than in islets and not vastly d
ifferent in islets and purified beta-cells. No sizeable amylase activi
ty was found in purified non-beta cells. In sections of rat pancreatic
tissue, immunocytochemistry documented the presence of amylase-like m
aterial in acinar cells and islet beta-cells and its virtual absence i
n non-beta islet cells. These findings were confirmed in dispersed isl
et cells also examined by double immunofluorescence of alpha-amylase a
nd either insulin or glucagon. The unexpected presence of amylase acti
vity in islet beta cells is considered in the perspective of both thei
r ontogeny and the metabolism of glycogen in these cells.