METHIONINE-ENKEPHALIN IN BONE AND JOINT TISSUES

Methionine-enkephalin (met-enk), an endogenous opiate, mimics many of the effects of morphine by binding to opiate receptors, thereby elicit ing similar cellular and behavioral effects, Using biochemical and imm unohistochemical techniques, several peptides have been identified in bone and joint tissues, Here we report, for the first time, the presen ce as well as concentration of met-enk in bone and joint tissues, Immu nohistochemistry using electron and immunoflourescence microscopy show ed cellular and neuronal distribution of met-enk in bone and joint tis sues, The concentration of met-enk analysed by high performance liquid chromatography electrochemical detection or radioimmunoassay was high in bone marrow, periosteum, ankle joint tissue, and cortical bone, An alysis by fast atom bombardment mass spectrometry suggested that the r ecovered fragment was met-enk. Administration of met-enk inhibits oste oblast cell growth in culture which is reversible by naltrexone. In ar thritic rats, the concentration of met-enk was significantly decreased in ankle joints compared with controls, suggesting a role for met-enk in the pathophysiology of adjuvant arthritis.