Induction of liver and lung tumours in rats by the simultaneous administration of sodium nitrite and morpholine

Long-term feeding studies were conducted in Sprague-Dawley rats using various dietary concentrations (up to 1000 ppm each) of nitrite and morpholine or 5 or 50 ppm N -nitrosomorpholine. The animals fed nitrite and morpholine at moderate to high concentrations developed hepatocellular carcinomas and angiosarcomas, histologically identical to those induced by preformed N -nitrosomorpholine. The data suggest that in vivo nitrosation of morpholine does occur in the rat, presumably in the acidic gastric environment.