Abstract
Glucose-6-phosphatase*has been demonstrated in pancreatic B cells of rabbit, guinea pig and dog, and in canine ductular epithelium. Short fixation of fresh frozen cryostat sections in cold neutral 6% calcium formol does not inhibit its activity or alter its distribution in liver or pancreas. Furthermore, specificity of the histochemical reaction for glucose-6-phosphatase was demonstrated by differences in staining when other substrates were incubated at the same pH for equal time. In view of the known relationship of blood sugar concentration to rate of insulin secretion, a hypothesis is advanced relating the presence of this enzyme in j3 cells to control of insulin secretion. It is suggested that the net rate of glucose-6-phosphate formation is the controlling factor and that this would be influenced by any increase or decrease of glucose-6-phosphatase activity.