ULTRACYTOCHEMICAL LOCALIZATION OF OUABAIN-SENSITIVE K-DEPENDENT PARANITROPHENYLPHOSPHATASE IN RAT SCIATIC-NERVE FIBERS()

In order to reveal and characterize Na+,K+-ATPase distribution in axon -myelin-Schwann cell units of sciatic nerves of adult and 15 days old Wistar rats, the ultracytochemical lead-paranitrophenylphosphatase tec hnique was used. The activity of K+-dependent paranitrophenylphosphata se, a component of Na+,K+-ATPase, was found on the cytoplasmic side of the axolemma and Schwann cell plasma membrane, as well as on the majo r dense lines of the myelin sheath. K+-paranitrophenylphosphatase acti vity was localized also at the axoplasmic profiles and at the Golgi ap paratus of the Schwann cells. Ouabain inhibition made it possible to d istinguish alpha 1 from alpha 2 and alpha 3 isoforms of Na+,K+-ATPase. The results suggest that the activity of the axolemma and myelin shea th is determined by alpha 2 and alpha 3 isozymes. The enzyme activity of the Schwann cell plasma membrane and Golgi complex was not visibly influenced by ouabain. These results suggest that the activity of thes e glial structures is determined mainly by alpha 1 isozyme.