THE INFLUENCE OF DIET ON THE PRODUCTION OF TUMORS OF THE LIVER BY BUTTER YELLOW

Un Tumore Primitivo Epatico a Diffusione Epizootica Nella Trota Iridea di Allevamento (Salmo Irideus)

Macroscopic and microscopie features, geographic distribution and incidence of a liver tumour in iridaceous trouts are described.

The tumour appeared first as a sporadic one in some breeding institutions of Italy and subsequently reached a high incidence rate (more than 50 per cent).

It has a hepatocellular trabecular structure with some scirrhoid patches.

Cholangiomatous and cholangio-carcinomatous areas are rare. Metastases were observed in the kidney, heart, gastric wall, and so on. No parasites and no cellular inclusions were found. Attempts to transmit the tumour to animals of the same strain by transplant of fragments or by injection of acellular extracts or by living together of affected animals with normal ones gave no results.

Genetic factors in some strains of iridaceous trouts bred in Italy may have played a role in the large diffusion of the tumour, through a high inbreeding. The traumatic lesion of the liver during the squeezing of the sexual product may represent an extrinsic factor realizing the carcinogenic potentiality through the nodular hyperplastic and regenerative processes produced by such manipulation.

THE PATHOGENESIS OF TUMORS OF THE LIVER PRODUCED BY BUTTER YELLOW

A conspicuous feature of the cirrhosis that is produced by butter yellow is the new formation of bile ducts that sprout from ducts of the larger portal spaces and penetrate between "portal units" to anastomose with liver cell columns at the periphery of these units. Hyperplasia of the liver may occur with butter yellow administration in the absence of cirrhosis or other change associated with widespread destruction of liver tissue; it occurs as diffuse or focal lesions and affects both parenchymal cells and newly formed ducts. Focal hyperplasia is a precursor of trabecular and adenomatous hepatomas which arise as multiple tumors. Butter yellow causes localized cystic dilatation of newly formed bile ducts unaccompanied by acute or chronic inflammation and liver cells adjacent to them may undergo hyperplasia. Cystic ducts by proliferation of their epithelium may form cyst-adenomas. Butter yellow causes newly formed ducts to undergo dilatation, and with acute inflammation and fibrosis to produce circumscribed macroscopically recognizable lesions (cholangiofibrosis). Cholangiofibrosis is the precursor of tumors that reproduce the histological characters of small bile ducts (cholangiomas), and often proceed to the formation of scirrhous carcinoma. Hepatomas, cyst-adenomas, and cholangiomas may become malignant with formation of metastases in which the characteristics of the parent tumor are reproduced.

CIRRHOSIS OF THE LIVER IN "DONOR" DOGS FED A HIGH FAT DIET AND SUBJECTED TO REPEATED BLEEDINGS

1. In 13 dogs used repeatedly as donors for plasmapheresis and plasma injection experiments and fed a kennel diet that for a period of over a year consisted chiefly of bones with much adherent fat, cirrhosis of the liver occurred in 10. Marked fatty change without definite fibrosis occurred in 2 of the dogs. 2. In control dogs fed the same kennel diet during the same period but not subjected to repeated bleedings, no instance of cirrhosis was observed. 3. In previous plasmapheresis and plasma injection experiments "donor dogs" subjected to similar bleedings over comparable periods but maintained on a different kennel diet did not develop cirrhosis. 4. This series of events suggests that in dogs maintained on a relatively high fat diet repeated bleedings predispose them to cirrhosis of the liver. No data are available to decide the more fundamental question: Do the repeated bleedings remove something (other than hemoglobin) necessary for continued integrity of the liver, or is the cirrhosis the result of relative anoxia or increased lipemia occasioned by the repeated bleedings or perhaps of both combined?

BP metabolism and the in vivo binding to hepatic DNA of rats fed diets containing menhaden fish oil

It is well established that dietary polyunsaturated omega-6 fatty acids promote tumorigenesis and support the activity of mixed-function oxidases (MFO), which are responsible for carcinogen activation. This study was undertaken to determine if increased levels of dietary menhaden fish oil (rich in omega-3 fatty acids) would affect in vivo binding of [3H]benzo[a]pyrene (BP) to rat liver DNA. The effects of dietary menhaden oil on the activities of phase I and phase II drug-metabolizing enzymes were also studied to determine the possible relationships between the activity of these enzymes and the binding of [3H]BP metabolites to liver DNA. Following a single intraperitoneal injection of [3H]BP, more BP was bound to liver DNA recovered from rats fed diet containing 20% menhaden oil for 11 days at all time intervals tested (16, 24, 48, and 192 hours) than was bound from rats fed 0.5% menhaden oil. The increased binding of [3H]BP to liver DNA of rats fed the high level of menhaden oil may be due, in part, to increases in the MFO responsible for BP activation (as suggested by increased cytochrome P-450 level and total BP hydroxylase activity). The higher concentrations of radioactivity extracted from blood of rats fed 20% menhaden oil diet at the initial time periods (16 and 24 hours) may be a reflection of the greater capacity of the liver to metabolize BP to more water-soluble metabolites. The maximum velocity (Vmax) for ethoxycoumarin O-dealkylase, expressed as nanomoles per milligram protein or per gram liver, was increased three- to fourfold by feeding the high level of menhaden oil. The differences in these enzymatic responses suggest that certain form(s) of cytochrome P-450 are preferentially increased by feeding the omega-3 fatty acids of menhaden oil.

MOBILIZATION OF BASOPHILE SUBSTANCE (RIBONUCLEIC ACID) IN THE CYTOPLASM OF LIVER CELLS WITH THE PRODUCTION OF TUMORS BY BUTTER YELLOW

Butter yellow (dimethylaminoazobenzene) causes degenerative changes in liver cells accompanied by chromatolysis of cytoplasmic structures that stain with basic dyes because they contain ribonucleic acid. These changes are profoundly modified by the protein content of the diet. Chromatolysis is succeeded by focal regeneration with reaccumulation of ribonucleic acid in the cytoplasm of liver cells; these foci of basophile hyperplasia have their origin in the parenchyma surrounding portal spaces and consist of cells arranged in columns or as tubules with lumina. Hepatomas arise from foci of basophile hyperplasia and corresponding with the arrangement of cells in these foci may be trabecular or adenomatous. Butter yellow causes new formation of bile ducts which arise chiefly in the immediate neighborhood of secondary portal spaces and produce the precancerous lesion, designated cholangiofibrosis. These bile ducts may accumulate ribonucleic acid in their cytoplasm and undergo hyperplasia. Cholangiomas arise from newly formed bile ducts that are the site of basophile hyperplasia. Changes accompanying chromatolysis and basophile hyperplasia aid in the definition of structural elements of the cytoplasm and in the localization of ribonucleic acid with relation to the mitochondria.