ALPHA-ISOZYMES AND EPSILON-ISOZYMES OF PROTEIN-KINASE-C IN THE CHONDROCYTES IN NORMAL AND EARLY OSTEOARTHRITIC ARTICULAR-CARTILAGE

Protein kinase C (PKC) isozymes (alpha, beta I, beta II, gamma and, ep silon-PKC) were examined immunocytochemically in control and mechanica lly induced osteoarthritic knee joints in rats. beta I, beta II, and g amma PKC-positive cells were not observed in sham-operated or osteoart hritic knee joints. alpha-PKC, which was observed only in the cells in the subchondral bony layer in the controls, appeared in the chondrocy tes in the superficial and columnar layers of the osteoarthritic knees . epsilon-PKC was observed in the control chondrocytes in the superfic ial portion of the columnar layers. In early osteoarthritic joints, ho wever, epsilon-PKC-positive chondrocytes disappeared from the superfic ial portion of columnar layer and increased in number in the middle co lumnar layers. The appearance and changes in distribution of these PKC -positive chondrocytes, either under normal or osteoarthritic conditio ns, have not been reported previously. The role of the redistribution of PKC isozymes is still unclear as to whether they are involved in in itiating destructive processes, reflect attempted cell repair mechanis ms, or are simply a consequence of the cellular changes.