The effects of nitric oxide on chondrocytes and lymphocytes.

ConcanavalinA (ConA)-activated lymphocytes markedly induced the production of nitric oxide from chondrocytes. The nitric oxide significantly inhibited the proliferation of both the chondrocytes themselves and the lymphocytes. When culture supernatant from ConA-activated lymphocytes was added to culture of chondrocytes, a large amount of nitric oxide was produced. NG-monomethyl-L-arginine (MMA) significantly eliminated both the production of nitric oxide and the inhibition of chondrocyte and lymphocyte proliferation. Furthermore, when MMA was added to the mixed culture of chondrocytes and lymphocytes with ConA, their proliferation was markedly enhanced compared with individual summation. These results indicate that chondrocytes produce not only nitric oxide but also a lymphocyte stimulating factor, the effects of which are, however, usually masked by the nitric oxide.