An enzymatic assay for myo-inositol in tissue samples

An enzymatic assay for myo-inositol (MI) was modified. The method is based on the oxidation of MI by NAD(+)-dependent MI dehydrogenase, coupled to reoxidation of NADH by iodonitrotetrazolium chloride and diaphorase. The resultant formazan is measured spectrophotometrically. In order to remove interference by glucose, preliminary phosphorylation of glucose by hexokinase was employed before the above reaction. The assay is quantitative for MI in amounts ranging from 1 to 20 nmol. This method gives a negligible blank, even in the measurement of rat serum. The reduced MI content in the sciatic nerve and lens of streptozotocin-induced diabetic rats recovered in a dose-dependent manner by treatment with a novel potent aldose reductase inhibitor, GP-1447 ¿3-[(4,5, 7-trifluorobenzothiazol-2-yl)methyl]-5-methylphenylacetic acid¿.