ABSTRACT
The levels of hexokinase, as well as those of the cytoplasmic glycolytic enzyme lactate dehydrogenase and the mitochondrial tricarboxylic acid cycle enzymes fumarase and citrate synthase, have been determined in whole rat brain and in neuronal, astrocytic, and oligodendroglial fractions isolated from rat brain. Compared with either whole brain or with isolated neurons or astrocytes, oligodendroglia are low in hexokinase content. This provides direct confirmation for the conclusion, based on an electron microscopic immunohistochemical method, that oligodendroglia, compared with other neural structures, contain relatively low levels of this key enzyme of glucose metabolism. Based on this confirmation, it is concluded that the electron-microscopic immunohistochemical procedure provides a valid indication of hexokinase content, and thus that other structures shown to stain weakly by the latter technique (e.g., dendritic terminals of cerebellar granule and Purkinje cells) are, indeed, low in hexokinase activity.
Subject(s)
Astrocytes/enzymology , Brain/enzymology , Hexokinase/metabolism , Neuroglia/enzymology , Neurons/enzymology , Oligodendroglia/enzymology , Animals , Citrate (si)-Synthase/metabolism , Female , Fumarate Hydratase/metabolism , L-Lactate Dehydrogenase/metabolism , Male , Rats , Rats, Inbred Strains , Synaptosomes/enzymologyABSTRACT
The fate of two water-insoluble (WI) dichlorobenzidine-based pigments, chlorodiane blue (CDB) and pigment yellow 12 (PY12), and of their sulfonated water-soluble (WS) analogs was studied in male Fischer 344 rats. Water-soluble analogs of chlorodiane blue and pigment yellow 12 were synthesized in order to study the effect of water solubility on the absorption and metabolism of dichlorobenzidine-based pigments. [14C]WI-CBD, [14C]WI-PY12, and the water-soluble analogs [14C]WS-CDB and [14C]WS-PY12 were administered by gastric intubation or dermal application at doses of 1.24-2.65 mumol/kg. Neither [14C]WI-CDB nor [14C]WI-[Y12 could be detected in any tissue at time points up to 1 d. The entire dose was accounted for in the feces after oral administration, and at the application site after dermal administration. Water-insoluble CDB is a component of a photoconductor (Weaver, 1981). Approximately 4.1% of [14C]CDB was observed and located primarily in the urine and liver after oral administration, but no detectable amount was absorbed after dermal application. Metabolites of [14C]WS-CDB identified in the urine were 3,3'-dichlorobenzidine diacetate, 3.3'-dichlorobenzidine and its glucuronide conjugate, and 3,3'-dichlorobenzidine monacetate and its glucuronide conjugate. Only 0.02% of [14C]WS-PY12 was absorbed after oral administration. Thus, some degree of water solubility was prerequisite for even a small amount of absorption or metabolism in vivo.