[Effects of the environment on the liver and gastrointestinal tract]

The liver has a central role in the detoxication and elimination of toxic substances which enter the body as lipid-soluble compounds. Their transformation into polar watersoluble metabolites, termed biotransformation, is bound to the membranes of the smooth endoplasmatic reticulum. The oxidating enzyme in biotransformation can be induced by certain toxins and drugs. The chronic induction of enzymes by DDT and the consequences of this process of adaptation, particularly in regard to the metabolism of calcium is discussed. The protective effect of biotransformation and induction of enzymes against carcinogens, especially aflatoxin, are briefly reviewed. As examples of the chronic influence of vasotoxic substances, mention is mode of the veno-occlusive disease caused by the alkaloid phlorrhizidin found in plants, and the vinyl-chloride disease occurring in workers handling PVC. The first leads to portal hypertension of the post-sinusoidal type, while the second leads to pre- or intrasinusoidal portal hypertension and, after years of exposure, to hemangioendotheliosarcoma of the liver. The same tumor has been observed after arsenic intoxication. Arsenic may also lead to non-cirrhotic portal hypertension. The present opinions about environmentally induced gastrointestinal diseases are widely hypothetical. The high frequency of gastric carcinoma in Japan. and the varying occurrence of carcinoma of the colon in the civilized world in comparison with the rural population of tropical regions, is emphasized. The explanation for these facts is probably to be sought in differences of nutrition.