Ethanol metabolism by a transplantable hepatocellular carcinoma. Role of microsomes and mitochondria

1. Ethanol metabolism in slices or homogenates of transplantable hepatocellular carcinoma HC-252 (HC-252) was 50 to 60% of the rate found in host liver slices or homogenates when they were expressed per gram of tissue wet weight and 70 to 80% of the liver when the rates were expressed per milligram of tissue protein. At 10 mM ethanol, the activities of alcohol dehydrogenase in tumor and liver supernatants were comparable. 2. Tumor microsomes did not oxidize ethanol in the presence of a NADPH-generating system, indicating the absence of the microsomal ethanol-oxidizing system and catalase-mediated peroxidation of ethanol. The HC-252 microsomes were contaminated with catalase, and acetaldehyde production occurred in the presence of a H2O2-generating system (xanthine oxidase). The virtual absence of ethanol oxidation and drug metabolism (aminopyrine demethylase and aniline hydroxylase) in HC-252 microsomes may be due to the low activities of NADPH-cytochrome c reductase, NADPH oxidase, and NADPH-dependent oxygen uptake. 3. Microsomal oxidation of ethanol was present in Morris hepatoma 5123C, a well-differentiated tumor of intermediate growth rate, while activity was negligible in microsomes from Morris hepatoma 7288CTC, a less differentiated tumor. Microsomal NADPH oxidase was present in the well differentiated tumor 5123C but was lacking in the less differentiated tumor 7288CTC. Several microsomal, mitochondrial, and cytosolic properties of HC-252 are similar to those of Morris hepatoma 7288CTC but differ from those of the more differentiated 5123C tumor and normal liver. 4. The content of mitochondrial protein in HC-252 was only 25% that of liver, and oxygen consumption per gram of tumor was only 28% that of the liver. When corrected for the mitochondrial protein content, oxygen uptake in tumor HC-252 and liver homogenates was comparable. Isolated tumor and liver mitochondria displayed comparable State 4 and 3 rates of oxygen consumption with succinate and glutamate as substrates. The activities of the reconstituted malate-aspartate and alpha-glycerophosphate shuttles were only slightly lower in isolated HC-252 mitochondria compared to liver mitochondria, when shuttles were reconstituted with purified enzymes. 5. Antimycin inhibited alcohol metabolism,and pyruvate stimulated alcohol metabolism, much less in tumor slices than in liver slices, suggesting the presence of an augmented mitochondria-independent, cytosolic mechanism for oxidizing reducing equivalents in the tumor. These factors suggest that oxidation of NADH is the limiting factor in ethanol metabolism. Whereas, in the liver mitochondrial reoxidation is predominant, in HC-252, cytosolic reoxidation of NADH also plays a major role.

Siderosis of lymph nodes patients with Hodgkin's disease

Lymph nodes removed from 28 untreated patients with Hodgkin's disease all contained markedly increased amounts of hemosiderine, whether or not they were histologically involved in the disease. This finding was particularly striking in patients with the nodular sclerosis type of disease. Abnormal deposits of iron were also noted frequently in lymph nodes containing metastatic carcinoma, lymphoma of non-Hodgkin's type, and reactive hyperplasia, but in each case, with the exception of metastatic squamous cell carcinoma, the amount was significantly less than seen in Hodgkin's disease. The findings suggest that in patients with Hodgkin's disease and perhaps in those with other disorders in which abnormal tissue retention of iron underlies sideropenic anemia, lymph nodes are an important site of iron retention.

Sequential phenotypic and biochemical alterations during chemical hepatocarcinogenesis

Chronic exposure to chemical carcinogens induces in the target tissue a series of complex morphological and biochemical alterations that precede the appearance of overt cancer. Three types of experiments are described: (a) exposure of livers that had received subcarcinogenic doses of N-2-fluorenylacetamide to a subcarcinogenic dose of dimethylnitrosamine resulted in a 100% yield of neoplastic nodules and hepatocellular carcinoma: (b) neither normal hepatocytes nor those obtained from neoplastic nodules were agglutinated by any of the lectins tested. This finding was also true for slowly growing cells from carcinomas, while those of rapidly growing carcinomas were agglutinated by several lectins; (c) analysis of nonhistone proteins isolated from neoplastic nodules demonstrated the appearance of many new species in euchromatin when compared with normal liver. Carcinomas demonstrated an even greater number of new species and they were demonstrated in heterochromatin as well.

Isolation and characterization of two alpha1-protease inhibitors in rat serum

Two alpha1-protease inhibitors were identified in rat serum. On polyacrylamide gels, one (R-I) appeared at the leading edge of the albumin, the other (R-2) at the trailing edge. The two inhibitors have differing molecular weights, differing inhibitory spectra toward proteases, and are immunologically distinct. The assays for antiprotease activity were performed on whole human and rat sera and inhibitor-enriched fractions of rat serum that had been electrophoresed on polyacrylamide gels. The more rapidly migrating antiprotease of rat serum, R-I, inhibited trypsin, chymotrypsin, and elastase. The more slowly migrating antiprotease, R-2, inhibited both trypsin and chymotrypsin but possessed only weak anti-elastase activity. When a comparison was made between human alpha1-antitrypsin and the more rapidly migrating rat inhibitor, it could be seen that they have similar molecular weights, similar inhibitory spectra, and similar electrophoretic mobilities. The relevance of the study of the R-I inhibitor in the pathogenesis of experimental emphysema is emphasized.

Sequential analysis of transplantable hepatocellular carcinomas

In a previous study multiple characteristics of chemically induced primary hepatocellular carcinomas were described and examined during the initial transplant generations. The present communication reports on these characteristics in subsequent transplant generations followed over a 2-year period. In almost all instances the growth rate, morphology, chromosome composition, and plasma protein and alpha-fetoprotein synthesis of individual tumors have remained relatively constant. However, one spontaneous subline of a diploid tumor demonstrated a sudden extensive rearrangement of its chromosomes simultaneous with a significant acceleration of growth rate. Despite karyotypic evolution, it retained the functional characteristics of diploid tumors, producing no plasma protein or alpha-fetoprotein.

Concanavalin A agglutination of cells from primary hepatocellular carcinomas and hepatic nodules induced by N-2-fluorenylacetamide

A previous study demonstrated that cells of transplantable hepatocellular carcinomas were agglutinated by the plant lectin concanavalin A, while normal hepatocytes were not. In the present experiments, 95% or more of cells obtained from primary hepatocellular carcinomas which resulted from exposure of rats to N-2-fluorenylacetamide were agglutinated by this lectin. Exposure to this carcinogen also produces grossly visible foci of morphologically and biochemically altered hepatocytes which have been termed hepatic (hyperplastic; premalignant, neoplastic) nodules. Although these hepatocyte aggregates are generally accepted as precursors of the hepatocellular carcinomas, no agglutination was detected when their cells were exposed to concanavalin A. These results indicate that concanavalin A agglutinability is not acquired as a result of tumor transplantation. Furthermore, they suggest that significant alterations must occur in the cells of hepatic nodules prior to the manifestation of malignant behavior.

Alteration of hepatocytes by subcarcinogenic exposure to n-2-fluorenylacetamide

These experiments examined the effects of a single, subcarcinogenic dose of dimethylnitrosamine or N-hydroxyfluorenylacetamide when administered after a subcarcinogenic dietary regimen of N-2-fluorenylacetamide. Control rats that received either carcinogen diet alone or a single dose of carcinogen demonstrated neither hepatic nodules nor hepatocellular carcinomas. Those animals that received dimethylnitrosamine subsequent to carcinogen diet demonstrated many persistent hepatic nodules and 100% hepato-cellular carcinomas. These data support the concept that the nodules produced by subcarcinogenic ingestion of N-2-fluorenylacetamide are not composed simply of normal hepatocytes undergoing compensatory regeneration but consist of cells that have been altered by the carcinogen. One manifestation of this alteration is an increased susceptibility to further carcinogenic evolution.

A study of alpha1-fetoprotein levels during exposure to 3'-methyl-4-dimethylaminoazobenzene and its analogs

The serum concentration of alpha1-fetoprotein (alpha1F) was determined in rats following exposure to the hepatocarcinogen, 3'-methyl-4-dimethylaminoazobenzene, and its analogs. Small quantities of the carcinogen caused a rapid and significant elevation of alpha1F. Neither 2-methyl-4-dimethylaminoazobenzene nor p-aminoazobenzene resulted in any elevation of alpha1F. Further, under circumstances wherein 2-methyl-4-dimeth-laminoazobenzene is reported to become carcinogenic, i.e., when administered at the time of 70 percent hepatectomy, neither elevation of alpha1F nor histological alteration of the liver was noted. The increase in alpha1F after 3'-methyl-4-dimethylaminoazobenzene exposure is the result of a highly selective interaction. The possible contribution of hepatocyte mitosis to the elecation of alpha1F seen during chemical carcinogenesis is emphasized.

Regulation of spleen growth and portal pressure in hepatic shcistosomiasis

Growth rate and histology of splenic autotransplants in subcutaneous pockets were compared with those of autotransplants in the extrahepatic portal bed in splenectomized mice infected with cercariae of Schistosoma mansoni and in splenectomized uninfected controls. By the fifteenth week after transplantation (and tenth week after injection of cercariae) subcutaneous transplants gained 6.5 times and omental transplants 8.2 times more weight in infected animals than corresponding transplants in uninfected animals. Portal pressures averaged 11 to 13 cm of water in infected animals with transplants and 17 cm in those with intact spleens (compared to that of 6 to 7 cm in controls). Hyperplasia of white pulp with increase in germinal center activity characterized transplants as well as intact spleens of infected animals. The results suggest that a) During the first 10 weeks of experimentally induced infection, portal congestion is not the predominant mechanism regulating increased spleen growth; and b) An intact enlarged spleen appears to contribute to elevated portal pressure.

Differential lectin agglutination of fetal, dividing-postnatal, and malignant hepatocytes

Numerous studies have reported the capacity of the lectin, concanavalin A, to agglutinate selected cell-types. The finding that cells transformed in culture, embryonic cells, and malignant cells are all agglutinated by this substance, may contribute to our understanding of the oncogenic process. The present study compared the response to concanavalin A of rat hepatocytes derived from livers of differing developmental and mitotic-status as well as those derived from malignant liver tumors (hepatomas). Fetal hepatocytes and hepatoma cells were highly susceptible to agglutination while hepatocytes from post-natal livers, whether dividing or quiescent, were not. Treatment with protease(s) did not make the interphase hepatocyte agglutinable. These data emphasize the importance of examining a wide variety of cells in attempting to understand the interaction of lectins on cell surfaces, and further, demonstrate the value of obtaining cells directly from tissue(s) during differing physiologic and pathologic states.

Regulation of spleen growth in heaptic dysfunction

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Hepatoma--nature's model tumor. A review

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Fluorescent banding patterns of rat chromosomes in normal cells and primary hepatocellular carcinomas

Quinacrine staining permits identification of rat chromosomes in metaphase that were formerly classified only in groups within the karyotype. This technique defined two types of abnormal chromosomes in cells of rat hepatomas.

Regeneration of the mammalian liver. VI. Retention of phenobarbital-induced cytoplasmic alterations in dividing hepatocytes

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L-asparaginase: inhibition of early mitosis in regenerating rat liver

L-Asparaginase in agouti serum and in extracts from Escherichia coli inhibits the early wave of mitosis occurring in rat liver approximately 30 hours after hepatectomy, but even with continued treatment of the animal the later wave at 50 hours is not inhibited. This result differs from the permanent inhibition of growth which asparaginase causes in various tumors.

Regeneration of the mammalian liver. V. Mitotic division in cytologically differentiated liver cells

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