Uptake and metabolism of 5-methyltetrahydrofolic acid by rat brain slices

Activity of 5-formyl tetrahydrofolate cyclodehydrase and 5,10-methenyl tetrahydrofolate cyclohydrolase in primary brain tumors in children

The activity of the enzymes 5-formyl tetrahydrofolate cyclodehydrase and 5,10-methenyl tetrahydrofolate cyclohydrolase has been studied cytochemically in children's primary brain tumors. These enzymes play a significant role in purine biosynthesis. Thirty children, aged 1-12 years, were studied, 12 with medulloblastoma, 14 with glioma grade I-IV, and 4 with ependymoma. The activity of the enzymes was apparent as cytoplasmic granules that sometimes overlie the nucleus of the tumor cells. This coincidence showed that different types of brain tumors exhibit different degrees of enzymic activity, which in some cases correlated positively with the malignant potential of the tumor. Approximately one third of the cases were negative for any activity of these enzymes. The intensity of the staining of 5,10-methenyl tetrahydrofolate cyclohydrolase activity was actually higher than that of 5-formyl tetrahydrofolate cyctodehydrase. The clinical or prognostic significance of these findings remains to be clarified, but we believe that cylochemistry provides a sensitive technique for the detection, localization, and description of these enzymes in brain tumor cells. A clear understanding of the mode of action of these enzymes may contribute to devising novel therapeutic strategies.

Effect of diet on folates levels and distribution in selected tissues of the rat

A technique for the extraction, purification and concentration of folates, followed by high performance liquid chromatography assay with fluorometric detection of the three principal derivatives (tetrahydrofolic, 5-methyl-tetrahydrofolic and formyl-tetrahydrofolic acids) has been applied to the determination of tissue folates in rats. The levels found are compared to those of the microbiological assay using Lactobacillus casei. When rats were fed a diet containing 1 mg of folic acid per kg of food, levels in the intestinal mucosae, liver, whole blood and brain were 0.59, 14.87, 0.28 and 0.83 nmol/g of tissue. An exogenous supply of 200 mg of folic acid/kg of food significantly increased folate levels in all tissues studied, except for the brain: 1.51, 28.93, 0.52 and 0.99 nmol/g, respectively in the above four tissues. The separation of the various derivatives and a variable supply of folic acid have enabled the conversions of these metabolites to be studied.