RELATION OF NA+, K+-ATPASE TO DELAYED MOTOR-NERVE CONDUCTION-VELOCITY - EFFECT OF ALDOSE REDUCTASE INHIBITOR, ADN-138, ON NA+, K+-ATPASE ACTIVITY

The role of sorbitol, myo-inositol, and Na+, K+-adenosine triphosphatase (ATPase) activity on motor nerve conduction velocity (MNCV) in streptozotocin (STZ)-diabetic rats was studied. Reduction of MNCV and Na+, K+-ATPase in caudal nerves appeared after 3 weeks of diabetes, and at this time treatment with aldose reductase inhibitor (ARI), ADN-138 and 1% myo-inositol supplement was begun. One percent myo-inositol supplement for 3 weeks resulted in a significant increase in myo-inositol levels in diabetic nerves, but left MNCV and sorbitol levels unchanged. In contrast, treatment with ADN-138 for 3 weeks reduced sorbitol levels in diabetic nerves and resulted in significant increases in MNCV and Na+,K+-ATPase in the nerves. Since ADN-138 did not restore myo-inositol levels, the increase in Na+, K+-ATPase levels by ADN-138 treatment was independent of myo-inositol levels. Also, nerve Na+ levels in ADN-138-treated rats were reduced and the ratio of K+ to Na+ was raised, while 1% myo-inositol supplement did not affect them. These results suggest that treatment with ADN-138 elevates MNCV through a series of processes: ARI → reduction of sorbitol level → increase in Na+, K+-ATPase activity → correction of K+, Na+ imbalance → increase in MNCV. © 1990.