Inhibition of aldose reductase: 13 C NMR studies in isolated peripheral nerve

We report 13 C NMR measurements of the flux through aldose reductase in isolated rat sciatic nerve, and its inhibition by an aldose reductase inhibitor of the sulphonylnitromethane class. [1‐ 13 C] galactose was used as substrate, and the rate of production of [1‐ 13 C] dulcitol was measured. Quantitation required the use both of internal extracellular, and external, standards. The mean net forward flux (±S.D) was 20±11 nmol/(mL nerve water)/min (n = 10). In the presence of the inhibitor, flux was reduced significantly (p<0.001) to 13% of control. Since dulcitol is symmetrical, an estimate of the backward flux, to [6‐ 13 C] galactose, is also possible; under our conditions, this was negligible.