Cytolytic activity of mineral oil elicited rat peritoneal macrophages activated by lipopolysaccharide (LPS) and/or rIFN-gamma, rIL-2, Zymosan and PMA (4-beta-phorbol-12-beta-myristate 13-alpha-acetate) was detected in the presence of various concentrations of L-arginine. This paralleled the NO2- production in the presence, but not in the absence, of L-arginine. Significant amount of NO2- was detected in the peritoneal macrophages cultured with 0.4 mmol of L-arginine 8 days and the last 24 h with LPS at a concentration of 1 microgram/ml. No significant differences were found between activated peritoneal macrophages obtained from normal (healthy) and/or from tumor bearing rats to induce tumoricidal activity and NO2- production under the same experimental conditions. The results showed that the major cytolytic mechanism against BP6-Tu2 and U 937 tumor cell lines is L-arginine-dependent nitrogen oxide synthesis of activated rat peritoneal macrophages.

Cancer Research Institute Slovak Academy of Sciences Bratislava Czechoslovakia