Cytotoxic carcinogeneic response to monocrotaline pyrrole.

The cytotoxic and carcinogenic effects of MCP, the possible proximate metabolite of the alkaloid monocrotaline, were investigated in rats by the subcutaneous route. Sequential of MCP subcutaneously produced an acute inflammatory reaction with necrosis of the local tissue. A slight delay in connective-tissue repair occurred and markedly enlarged fibroblasts were a distinctive feature of the lesion. Four injection site sarcomas were produced after repeated injection of 60 mug MCP in tricaprylin. Injection of 30 mug MCP in tricaprylin twice weekly gave rise to three local tumours. Controls injected repeatedly with tricaprylin developed two sarcomas at the injection site. The significance of these findings is discussed and it is concluded that MCP is undoubtedly cytotoxic but that its carcinogenic potency is equivocal.