Studies on the experimental arthritis in rats following the intravenous injection of peptidoglycan extracted from group A streptococcal cell walls

Abstract

Polyarthritis induced in rat using streptococcal peptidoglycan (PG) was investigated and the following results were obtained.
1) Polyarthritis was induced in normal rats within 1 to 2 days after a single intravenous injection of 1 mg PG extracted from group A streptococcal cell walls without mineral oil.
2) Rat platelets were suspended in homologous plasma or serum were incubated with PG, C-polysaccharide-PG complex (C-poly-PG complex) or synthetic N-acetylmuramyl-L-aranyl-Disoglutamine (MDP). Serotonin (5-HT) was released from rat platelets by the incubation with PG, however, it was not released when incubated with C-poly-PG complex or MDP.
3) The release of 5-HT from platelets by PG was inhibited when platelets were suspended in heat inactivated serum. This fact suggests that the process of releasing 5-HT from platelets is mediated through the activation of complement.
4) From microscopic examination, the synovial membrane revealed stasis of arteries and pen-vascular stasis within 3 to 6 hours after administration of PG. Moreover, proriferation and degranulation of mast cells in the pen-vascular space were sometimes observed. On the 3 rd day after administration, the round cell infiltration mainly consisted of neutrophiles and there was disintegration of the lining cells in synovial membrane. These results indicate the presence of acute inflammatory process in this stage.
5) Scanning electromicroscopy revealed that there were morphorogical changes in the platelets incubated with PG and extrusion of numerous pseudopodia.
In conclusion, the present data suggestes that the release of chemical mediators such as 5-HT and/or histamine by PG in situ may play an important role in inducing polyarthritis by PG.