Retrograde axoplasmic transport to inactive dopamine beta-hydroxylase in sciatic nerves.

The transport of dopamine-beta-hydroxylase (DBH) in sciatic nerves was studied both by measuring the accumulated enzyme activity and by examining the accumulated immunologically reactive DBH protein. The pattern of DBH accumulation in the proximal segment was similar either in the activity or in the immunofluorescence. In the distal segment, however, much higher accumulation of immunofluorescence than that of the activity was observed 7 h after ligation. The immunotitration studies indicated that more DBH molecules were accumulated in the distal segment than in the proximal segment 5 h after ligation. The homospecific activity of DBH in the distal segment was about one-fifth of that in the proximal segment. The result suggests that relatively large amounts of inactive enzyme may be transported back to the soma instead of complete degradation in the terminal.