ENZYME HISTOCHEMISTRY AND HORMONES OF DEVELOPING GASTROINTESTINAL TRACT OF CHICK EMBRYO .I. A HISTOCHEMICAL AND QUANTITATIVE STUDY OF GLYCOGEN, URIDINE DIPHOSPHATE GLUCOSE-GLYCOGEN TRANSGLUCOSYLASE, GLUCOSE-6-PHOSPHATASE AND PHOSPHORYLASE

Glucose-6-phosphate is an important metabolite which acts as the substrate linking three important metabolic cycles. The glycolytic pathway, the pentose cycle and the tricarboxylic acid cycle. The enzyme glucose-6-phosphatase which metabolises this substrate is therefore of key importance. This enzyme was found to fluctuate and to be highly sensitive to insulin during the differentiation of the gastrointestinal tract. The enzyme has the same localisation in the epithelium of the developing gut as glycogen, uridine diphosphate glucoseglycogen transglucosylase and phosphorylase. It increases in activity just before hatching when the absorptive functions of the gut start and may then assume this new function. The importance of uridine diphosphate glucoseglycogen transglucosylase and phosphorylase in the developing gastrointestinal tract is also discussed. © 1969 Springer-Verlag.