Galanin and Leu-enkephalin in the rat : with special reference to adjuvant arthritis

Abstract

In these studies, the tissue and cellular distribution of Galanin and Leu-enkephalin were demonstrated in normal bone and joints. Furthermore, tissue levels of Galanin and Leuenkephalin were also studied in the ankles and the spinal cord of arthritic rats. We used immunoeletronmicroscopy (iEM), to study cells and tissue compartments. Radioimmunoassay (RIA) was used to quantify the contents in periosteum, cortical bone and bone marrow in normal rats as well as in ankles and spinal cords of arthritic rats.

The results demonstrated that Leu-enkephalin is distributed abundantly in the sciatic nerve fibers and in monocytes of bone marrow and endothelial cells in the periosteum as well as in macrophagelike-cells of the synovial membrane. The concentration of Leu-enkephalin measured by RIA showed the highest concentration in bone marrow followed by periosteum and cortical bone in normal tissue. In arthritis, the increased level of Leu-enkephalin detected by iEM was shown in the matrix of the sciatic nerve, the nerve fibres in the synovial membrane and periosteum as well as in fibroblasts and endothelial cells of the periosteum. The concentration of Leu-enkephalin measured by RIA was lower in the ankle and increased in the spinal cord of arthritic animals compared with the controls. Galanin was abundant in nerve fibers and endothelial cells in the periosteum as well as in nerve fibers and in macrophage-like-cells of the synovial membrane. The concentration of galanin measured by RIA showed the highest concentration in bone marrow followed by periosteum and cortical bone. In arthritis, RIA showed the significantly lower level in the ankles and spinal cords of rats with adjuvant arthritis compared to controls. Our iEM results showed decreased galanin labelling in the sciatic nerve and in macrophage-like cells in the synovial membrane and increased labelling in monocyte lineage cells, polymorphonucleated lineage cells in the bone marrow, fibroblasts in the periosteum, osteoclasts and osteocytes, and lower labelling in osteoblasts in arthritic rats compared to controls.

Our results in general showed measurable levels of Galanin and Leu-enkephalin in bone and joint tissues, in adition to the abundency in the nervous system. The concentrations of both peptides was altered due to adjuvant arthritis.