IMMUNOCYTOCHEMICAL DISTRIBUTION OF CA2-INDEPENDENT PROTEIN-KINASE-C SUBTYPE-DELTA, SUBTYPE-EPSILON, AND SUBTYPE-ZETA IN REGENERATING AXONALGROWTH CONES OF RAT PERIPHERAL-NERVE()

In the peripheral nerve, regenerating axonal sprouts usually emanate a t nodes of Ranvier, and extend as growth cones along the inner surface of Schwann cells and/or through Schwann cell columns in the distal ne rve segment. In order to elucidate the significance of Ca2+-independen t protein kinase C in nerve regeneration, localizations of delta, epsi lon and zeta subtypes were examined immunocytochemically in sprouts an d growth cones of regenerating axons, as well as in normal intact nerv es in the rat sciatic nerve. In normal nerves, intense immunoreactivit ies of delta, epsilon and zeta subtypes were present in axons of both myelinated and unmyelinated fibres. Subcellularly, the distribution of these subtypes in the axoplasm was patchy, and discontinuous in the a xolemma and subaxolemmal peripheral zones of myelinated nerves. Some t hin myelinated axons showed no immunoreactivity for epsilon subtype. S chwann cells of both myelinated and unmyelinated fibres had moderate i mmunoreactivities for each subtype. In areas of nerve regeneration, ax onal sprouts at nodes of Ranvier, and growth cones extending along Sch wann cell basal laminae, had intense immunoreactivities for delta, eps ilon and zeta subtypes which are distributed diffusely throughout the axoplasm, and on the entire axolemma. In the sprouts, immunoreactivity for epsilon subtype was strong on the axolemma, but weak or almost ab sent in the axoplasm. These data, together with those of our previous study, indicate that Ca2+-independent protein kinase C subtypes (delta , epsilon and zeta) have basically the same distribution patterns as t hose of Ca2+-dependent subtypes in sprouts and growth cones of regener ating axons, as well as in normal intact axons; albeit epsilon subtype is somewhat different in distribution and intensity from delta and ze ta subtypes. It is suggested that Ca2+-independent subtypes are involv ed in maintaining growth cone activities along with the Ca2+-dependent subtypes. (C) 1997 IBRO. Published by Elsevier Science Ltd.