Increased plasma kallikrein activity and tumour growth suppression associated with intralesional bradykinin injections in hamsters.

Daily intralesional injections of bradykinin (250 microgram) into syngeneic SV40 virus-induced fibrosarcomas in inbred hamsters for 21 days produced marked inhibition of tumour growth, marked lymphoid cell infiltration of tumours, and significant elevations in plasma kallikrein and prekallikrein activity, compared with intralesional saline injections. All tumours were of comparable size and growth rates before injections were begun. Plasma kallikrein levels of animals which received the standard tumour cell inoculum subcutaneously and did not develop tumours were elevated significantly above normal levels and above levels of animals with large tumours. Kallikrein inhibitor activity of animals which did not develop tumours was depressed below normal levels. Intralesional injections of saline produced a significantly lesser response in plasma kallikrein and plasma prekallikrein activity than was encountered with subcutaneous saline injections in normal animals. Intralesional injections of bradykinin produced a response equivalent to that encountered with subcutaneous bradykinin injections in normal animals.