Enzyme changes in axon, myelin, and Schwann cells in injured sciatic nerve

Four enzymes related to specific cell functions were assayed in rat sciatic nerve injury by crush (cr) or crush and ligation (cr‐lig) after 2, 7, and 15 days in situ. Enzyme activities in segments of sciatic nerve proximal and distal to the injury were compared to those in corresponding segments of the contralateral nerve. Choline acetyltransferase (CAT) activity in the distal portion decreased by 65% for cr and almost to zero for cr‐lig by day 7, while in the proximal portions CAT decreased to 70% of control values by 7 days and to 50% at 15 days after cr‐lig. The activity of the Schwann cell–myelin‐associated enzyme 2′,3′‐cyclic nucleotide phosphohydrolase (CNP) decreased slowly distal to the injury. Distal to both types of injury the lysosomal enzyme beta‐glucuronidase (GLR) increased six‐ to eightfold by 15 days. Proximal to injury GLR also increased (P cr × 2.5, P cr‐lig × 5) but the peak proximally was attained by day 7. Despite interruption of axonally transported enzymes, the activities of the metabolic enzyme creatine kinase (CK) increased distal to injury apparently reflecting changes in the functions of the Schwann cells. The loss of metabolic enzymes from the axonal compartment may be completely obscured by reciprocal changes in the nonneuronal compartments if the activity is present in both compartments.