EFFECT OF SUPPLEMENTAL L-ARGININE IN A CHEMICAL-INDUCED MODEL OF COLORECTAL-CANCER

L-Arginine inhibits the development of spontaneous, transplantable sol id tumors and chemically induced mammary tumors. The aim of the presen t study was to investigate the effect of L-arginine on chemically indu ced colorectal cancer in male Wistar rats. Colorectal cancer was induc ed in all animals by weekly subcutaneous injections of the colonic pro carcinogen 1,2-dimethyhydrazine (DMH) at a dosage of 20 mg/kg body wei ght. Arginine was given in a 1% solution of drinking water. Group I wa s the DMH control; group II, arginine for 22 weeks; group III, arginin e for the first 10 weeks only. Lymphocyte function was evaluated by me asuring the thymic lymphocyte proliferative response to the T cell mit ogen phytohemagglutinin. The results show that tumor incidence and tum or burden (tumors/rat and tumors/tumor-bearing rat) were significantly reduced in both groups of animals receiving arginine compared to DMH controls (p < 0.05). The tumor areas and volumes were also reduced in both arginine groups (p < 0.05). Thymic lymphocyte stimulation indices were significantly increased by arginine supplementation (p < 0.05). These results would be in keeping with the reduction in colorectal tum or production due to a ''nonspecific'' stimulation of the host immune system by L-arginine.