DISTRIBUTION OF PROTEIN-KINASE-C (ALPHA-SUBTYPES, BETA-SUBTYPES, GAMMA-SUBTYPES) IN NORMAL NERVE-FIBERS AND IN REGENERATING GROWTH CONES OFTHE RAT PERIPHERAL NERVOUS-SYSTEM

The distribution of protein kinase C (alpha, beta, gamma subtypes) was studied using immunocytochemical techniques in normal nerve fibers an d in regenerating sprouts (growth cones) from the nodes of Ranvier fol lowing crush injuries to the rat peripheral nervous system. In normal nerves, for each protein kinase C subtype, immunoreactivity was presen t in both myelinated and unmyelinated axons. In myelinated axons, immu noreactivity for all three subtypes was patchy in the axoplasm and dif fuse in the subaxolemmal peripheral zones. No immunoreactivity was fou nd in the microtubule and neurofilament (cytoskeletal) domain. In cont rast, in unmyelinated axons, immunoreactivity was distributed diffusel y in the axoplasm. Schwann cells of myelinated fibers exhibited protei n kinase C immunoreactivity, but those of unmyelinated fibers did not. In regenerating nerves, early sprouts and growth cones extending thro ugh the crushed site along Schwann cell basal laminae exhibited intens e immunoreactivity for all three subtypes. Immunoreactivity was distri buted diffusely throughout the axoplasm of the regenerating sprouts (g rowth cones), in which microtubules and neurofilaments were very rare. Thus, the subcellular localization of the protein kinase C immunoreac tivity in growth cones of early regenerating nerves differed from that of normal parent axons. These findings suggest that protein kinase C (alpha, beta and gamma subtypes), whose subcellular distribution becom es more extensive in regenerating axons, may have important functional roles in axonal sprouting and in the regulation of growth cone activi ty in the peripheral nervous system.