STIMULATION OF ALPHA-(METHYLAMINO) ISOBUTYRIC ACID UPTAKE BY INTERLEUKIN-1 IN HUMAN SYNOVIAL-CELLS - INVOLVEMENT OF A CAMP-DEPENDENT PATHWAY

After one hour incubation with interleukin-1 beta (IL-1 beta), the upt ake of alpha-(methylamino) isobutyric acid (MeAIB) by human osteoarthr itic synovial cells appeared significantly increased. This effect, obs erved with 0.1 to 5 ng/ml of cytokine, was inhibited by cycloheximide, indicating that protein synthesis is involved. In addition, this effe ct seems mediated by a pertussis toxin-sensitive G protein. Finally, i ntracellular cAMP concentration measurements, the use of a phorbol est er, protein kinase inhibitors and forskolin+3-isobutyl-1-methylxantine (IBMX) provided evidence that a cAMP-dependent protein kinase is asso ciated with interleukin-1 beta-mediated alpha-(methylamino) isobutyric acid uptake.