Sensitivity of glucose 6-phosphatase activity to glutaraldehyde

The perinatal development of glucose-6-phosphatase activity distribution pattern in rat liver. A microdensitometrical study

The ontogenetic development of the intralobular distribution pattern of glucose-6-phosphatase activity in the rat liver is described in terms of histochemical changes determined with microdensitometry. A newly developed cerium-lead technique was employed and compared with the common lead technique optimized by Teutsch (1978a). The cerium technique has advantages, meets the prerequisites for quantitative determinations and yields results comparable to biochemically obtained data from microdissected tissue. The first signs of a heterogeneous distribution pattern of glucose-6-phosphatase activity are observed on the 3rd d after birth, and differences between periportal and centrolobular areas are largest around 10th and 15th d. At 30th d after birth, the adult pattern is complete with a centrolobular glucose-6-phosphatase activity of 67% of the periportal value.

Cytochemical localization of glucose-6-phosphatase activity in the central nervous system of the rat

The histochemical detection of glucose-6-phosphatase (G-6-Pase) in neurons of the CNS has been confirmed at the level of electron microscope. Both glucose-6-phosphate (G-6-P) and alpha-glycerophosphate (alpha-gP) can be used as substrates to localize the reaction product of this enzyme, which we have found in all cell types of the cerebral cortex, cerebellum and brain stem. The reaction was most prominent in large neurons, such as the Purkinje cells of the cerebellum and the pyramidal cells of the cerebral cortex. This is due to their extensive content of rough and smooth endoplasmic reticulum, the ultrastructural sites of G-6-Pase activity. It was possible to measure quantitatively the hydrolysis of G-6-P and alpha-gP in brain homogenates and also in microsomal fractions, the biochemical correlate of the cytochemically demonstrable activity. These results call for a reappraisal of the previous biochemical evidence, which negates the existence of brain G-6-Pase, and consequently a reassessment of current concepts pertaining to the metabolic regulation of brain glucose.