Depletion of myo-inositol and amino acids in galactosemic neuropathy.

A depletion of not only myo-inositol (MI) but also taurine and other amino acids was observed in the sciatic nerve of a galactosemic rat. Treatment of the galactosemic rats with sorbinil, an aldose reductase (AR) inhibitor, was found to block galactitol formation and protect against the loss of MI, taurine, and other amino acids. Incubation studies of sciatic nerve have revealed that [3H]MI and [3H]taurine were actively taken up and concentrated. Incubation of the nerve in a high-galactose medium showed a decrease in the accumulation of [3H]MI and [3H]taurine whereas the galactitol level increased. Time-course studies have shown that the galactitol level reached a plateau before a substantial decrease in the accumulation of [3H]MI and [3H]taurine occurred. The addition of AR inhibitors in the galactose medium significantly protected against the loss in the capacity of the nerve to accumulate [3H]MI and [3H]taurine. Hypertonicity of the galactose medium also seemed to have a protective effect similar to that of AR inhibitors.