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-paranitrophenyl-phosphatase technique was used. The activity of K(+)-dependent paranitrophenylphosphatase, 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 major dense lines of the myelin sheath. K(+)-paranitrophenylphosphatase activity was localized also at the axoplasmic profiles and at the Golgi apparatus of the Schwann cells. Ouabain inhibition made it possible to distinguish alpha 1 from alpha 2 and alpha 3 isoforms of Na+,K(+)-ATPase. The results suggest that the activity of the axolemma and myelin sheath 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 these glial structures is determined mainly by alpha 1 isozyme.