The uptake of horseradish peroxidase by damaged autonomic nerves in vitro.

The uptake of horseradish peroxidase by damaged autonomic nerves was studied in vitro. Large amounts of the enzyme penetrated the axons in a diffuse (nonvesicular) form. This occurred within 90 minutes of application of the enzyme. Twenty four hours after application of the enzyme diffuse peroxidase was still present in the axoplasm, but it was 'diluted' as a result of great axonal swelling. Pinocytotic uptake of the enzyme was observed both 90 minutes and 24 hours after application of the enzyme. The swollen axons close to the point of ligation showed most evidence of pinocytotic uptake, largely into coated vesicles, and much membrane-bound peroxidase reaction product was present. The uptake of peroxidase in a membrane-bound form may be of particular significance for the subsequent retrograde transport of the enzyme.