Coexistence of Nerve Conduction Deficit With Increased Na⁺-K⁺-ATPase Activity in Galactose-Fed Mice: Implications for Polyol Pathway and Diabetic Neuropathy

We measured motor nerve conduction velocity (MNCV), Na⁺-K⁺-ATPase activity, polyol-pathway metabolites, and myo-inositol in sciatic nerves from control mice, galactose-fed (20% wt/wt diet) mice, and galactose-fed mice given the aldose reductase inhibitor ponalrestat (300-mg/kg diet). Treatments were maintained for 4 wk. Galactose feeding was associated with a 21.5% reduction in MNCV (P < 0.001), which was almost completely prevented by ponalrestat. Galactose-fed mice showed an 81% increase in Na⁺-K⁺-ATPase (P < 0.01), an effect completely prevented by aldose reductase inhibition. Treatment of a separate galactose-fed group with sorbinil (300 mg/kg diet) also attenuated the MNCV deficit and prevented the increased Na⁺-K⁺-ATPase activity associated with galactosemia. Accumulation of galactitol in the nerves of galactose-fed mice was prevented by aldose reductase inhibition, but there were no alterations in myo-inositol levels in the sciatic nerves of any group. These data show that exaggerated flux through the polyol pathway can cause an MNCV deficit that is unrelated to either myo-inositol levels or Na⁺-K⁺-ATPase activity.