Rat serum lipoproteins during carcinogenesis of the liver in the preneoplastic and the neoplastic state

A comparative study of gene expression profiles in rat liver after administration of alpha-hexachlorocyclohexane and lindane

Alpha-hexachlorocyclohexane (alpha-HCH) is a stereoisomer of gamma-HCH, the active ingredient of lindane (> 99% gamma-HCH). In the present study, cDNA microarray technology was employed to identify changes in gene expression associated with toxicity in livers of male Fischer 344 rats after treatment with alpha-HCH (2, 20 mg/kg/day) and lindane (1, 10 mg/kg/day) by daily oral gavage for up to 28 days. Liver samples were obtained after 1, 3, 7, 14 and 28 days and compared for gene expression profiles. The dose of the alpha-HCH was higher than that of lindane and toxicity was greater, but the numbers of probe sets with differences in expression were fewer for the alpha-HCH-treated group except on Day 3. Only very few probe sets with differences in expression overlapped between alpha-HCH and lindane at each time point and the gene expression profiles were very dissimilar. Important liver-based differences in expression between alpha-HCH and lindane might possibly account for hepato-carcinogenicity of alpha-HCH.

The glycosphingolipid composition of the human hepatoma cell line,Hep-G2

The origin of plasma glycosphingolipids in normal individuals and the mechanisms by which tumor-associated glycosphingolipid antigens enter the plasma in patients with cancer are largely unknown. The Hep-G2 human hepatoma cell line retains many of the characteristics of differentiated hepatocytes including the ability to synthesize and secrete lipoproteins. Preliminary results indicated that newly synthesized Hep-G2 cell glycosphingolipids are coupled to the secreted lipoproteins. This suggests that this cell line may offer an interesting model for studying glycosphingolipid secretion, transfer, and shedding. We now report on the chemical and immunological characterization of Hep-G2 cell glycosphingolipids. Five major glycosphingolipids were purified and biochemically characterized: glycosylceramide, lactosyl ceramide, ceramide trihexoside, ganglioside GM3, and lactosyl sulfatide. Four additional minor components (3-fucosyl-lactosamine containing glycolipids, asialo GM2, galactosylgloboside, and ganglioside GM1) were identified using a combination of exoglycosidase digestion and immunostaining of thin-layer chromatography plates with specific carbohydrate binding proteins. This demonstrates that although this cell line synthesizes a limited number of major glycosphingolipids, it retains the ability to produce at least small amounts of structures in the lactoneo, globo, and ganglio series of glycosphingolipids. These studies show that it will be possible to investigate the mechanisms of secretion by Hep-G2 cells of different classes of these molecules such as neutral glycosphingolipids, gangliosides, and sulfatides.

Hepatic cholesterol in lead nitrate induced liver hyperplasia

Wistar rats treated with lead nitrate were used in these experiments to provide evidence of the possible correlation between hyperplasia, induced cholesterol synthesis and the levels of glucose-6-phosphate dehydrogenase (G-6-PD) in the liver. Lead treatment increases liver weight, hepatic cholesterol esters and the relative content of free cholesterol. An increase of the incorporation of tritiated water in free and cholesterol esters was also observed. The effect of lead resulted in an increase of hepatic G-6-PD at all times considered. The correlation between these parameters and hyperplasia are discussed.

Comparative serum apolipoprotein studies in ischaemic heart disease and control subjects

We have compared the concentrations of serum lipoprotein apoproteins in 55 ischaemic heart disease (IHD) patients and 116 apparently healthy control subjects by a simple, precise and reasonably sensitive "rocket" electroimmunoassay technique. Apolipoprotein B and apolipoprotein C levels in the vaery low density lipoprotein class and apolipoprotein B in the low density lipoprotein class were significantly lower IHD patients than in control subjects (p < 0.001). Apolipoprotein A levels within high density lipoproteins were markedly lower in a subpopulation of IHD patients compared with age-and sex-matched controls (p < 0.05). Using levels in excess of the 95th percentile of the levels in the healthy control population to delineate "abnormalities", we showed that there were more patients with "abnormalities" when lipoprotein apoprotein measurements were considered than when lipoprotein lipids were considered. The positive correlations between lipoprotein lipids and their apoproteins were in most instances greater in IHD patients than in controls.

Increase of serum very low density lipoproteins in rats after administration of alpha-hexachlorocyclohexane

After enteral administration of 200 mg/kg alpha-hexachlorocyclohexane (alpha-HCH) female Wistar rats develop a hyperlipemia. 48 h after administration of alpha-HCH, serum triglycerides are increased by 300%, whereas both serum cholesterol and serum total phospholipids only increase by about 45%. Serum free fatty acids are not significantly altered. Fractionation of the serum lipoproteins by ultracentrifugation shows that the hyperlipemia is due to a fivefold increase in serum very low density lipoproteins. Hepatic triglyceride secretion, calculated after i.v. injection of Triton WR 1339, is increased in animals pretreated wtih alpha-HCH. Corresponding to this observation, drugs known to diminish the triglyceride secretion of the liver, such as actinomycin D, cycloheximide; glucagon, orotic acid, CFT 1201, and CFT 1042 reduce the alpha-HCH-induced hyperlipemia. We concluded from the results that hyperlipoproteinemia after alpha-HCH is due to an increased hepatic very low density lipoprotein secretion. At the same time, the blood sugar level was decreased in fasting animals after treatment with alpha-HCH. Earlier experiments suggest that this effect is due to a decreased gluconeogenesis in the liver.

Major lipid classes in plasma membrane isolated from liver of rats fed a hepatocarcinogen

More phosphatidylethanolamine and less phosphatidylinositol were present in the lipid of plasma membrane isolated from the liver of rats fed a diet containing the hepatocarcinogen, N-2-fluorenylacetamide than were present in the lipid of plasma membrane isolated from the liver of rats fed the basal diet. Phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin from the former membranes had relative amounts of 18 : 1 in their fatty acyl profiles that were 1.5--1.7 times the relative amount of 18 : 1 in the same phospholipid from the latter membranes. Furthermore, the former membranes contained 1.3 times more cholesterol and 1.35 times more sphingomyelin than the latter membrames.

Carcinoma of the gallbladder: staging, treatment, and prognosis

Sixty-six cases of carcinoma of the gallbladder treated at The Memorial Hospital, Danville, Virginia, and the Medical College of Virginia, Richmond, were staged according to depth of invasion and spread and graded histologically; the findings were correlated with survival. Results from the two hospitals were essentially identical and the survival figures correlated well with 399 reported cases in the medical literature which could be staged according to the depth of invasion. A simple method combining staging and histologic grading of cancer of the gallbladder, which can easily be applied to all cancers of the gallbladder removed surgically and which should prove useful in the management of this disease, is described. Essentially all of the carcinomas of the gallbladder in the series were incidental findings at surgery for gall stones which may explain a relatively high proportion of superficial carcinomas which are cured by the removal of the gallbladder.

The influence of some dietary factors and/or treadmill exercise on rat and chicken tissue lipids and serum lipoproteins

Four different experiments, one with cockerels and three with rats, are described which relate to the effect of dietary factors and/or exercise on serum and liver lipids as well as on serum lipoproteins. Several classes of lipoproteins were isolated by preparative ultracentrifugation, and their purity assessed by gel electrophoresis. The lipid composition and protein content of serum lipoproteins and tissue were also determined. Dietary cholesterol produced an enormous increase (200 fold) in serum very low density lipoproteins in cockerels. This lipoprotein was apparently of very large particle size because it failed to penetrate the spacer gel during disc electrophoresis. In rats fed a cholesterol-supplemented diet, the increase in very low and low density lipoproteins was relatively insignificant in comparison with the cockerels. However, in both species, the liver was overloaded with cholesterol. Further, the serum high density lipoproteins, HDL2 were greatly diminished in both species as a result of cholesterol ingestion for 7 weeks. As a possible explanation for these related observations, it was proposed that HDL2 was utilized in the formation of cellular membranes by cholesterol-burdened, hyperplastic livers. A very high level of dietary corn oil (40% by weight) caused drastic changes in rat liver lipid levels and in serum lipoprotein profiles. Specifically, liver cholesterol and triglycerides were increased about 200% over normal. In another experiment, tissue lipids and serum lipoprotein levels were determined in treadmill-exercised rats and in sedentary controls. Two levels (4 and 40%) of a fat mixture (1:1, hydrogenated coconut oil: corn oil) were used in this study. The serum cholesterol was unchanged in the 4 groups, while the serum triglycerides were reduced in exercised rats given 4% but not 40% fat as compared to respective controls. Rats fed 40% fat and exercised had near normal levels of liver lipids which was in sharp contrast to their sedentary controls. The low denstiy lipoproteins were surprisingly higher in exercised rats given high fat than in sedentary controls. It was suggested that the direct synthesis of these lipoproteins by the liver may be necessitated under unusual conditions. In conclusion, considering the central role of liver in lipid and lipoprotein metabolism greater attention should be focused on this organ in future experiments on the control of hyperlipoproteinemia.

The influence of a high level of corn oil on rat serum lipoproteins

Although the stated requirement for linoleic acid in humans is less than 2% of the dietary calories, recently there has been considerable emphasis on the necessity to substitute dietary polyunsaturates for saturates in order to reduce serum cholesterol levels. In this study we have sought to determine the nutritional consequences of feeding a very high level of linoleate to rats. Three groups of thirty adult animals each were fed a semipurified diet consisting by weight of casein 17%; mineral mixture 5.5%; vitamin mixture in glucose 2.2%; cellulose fiber 3.0%; and corn oil 0% (group A), 10% (group B) or 40% (group C), which was provided at the expense of glucose. At the end of four weeks on the diets, blood was obtained in the fasting state from 16 rats in each group. The serum was ultracentrifugally fractionated into six classes of lipoproteins and analyzed for lipid composition and protein content. Disc gel electrophoresis using lipid and protein stains established that the various lipoprotein subclasses were reasonably free of adjacent density fractions. Although the total serum cholesterol levels were practically the same in the three groups, the cholesterol moiety of the major low density lipoproteins, LDL2 (d 1.019-1.050), but not of very low density lipoproteins, VLDL (d 1.006) or low density lipoproteins, LDL1 (d 1.006-1.019), was substantially and very significantly increased in rats fed the high level of corn oil as compared to the other groups. The concentration of the very low density lipoproteins was significantly lower in group C than in the groups A and B. The LDL2 concentration but not that of LDL1 was significantly greater in group C as compared to group A. The cholesterol/total lipid ratio was significantly greater in both LDL2 and LDL1 but not in VLDL of group C as compared with group A. The serum high density lipoproteins were relatively less influenced by the ingestion of an excessive level of corn oil at this time period. The serum lipoprotein levels as well as their lipid composition were generally similar in groups A and B and suggested that a moderate level (5%) of dietary linoleate did not cause any untoward changes in rats. On the basis of current information on the metabolism of lipoproteins, it has been proposed that the increase in rat serum LDL2 of group C reflects the status of the liver and that a large portion of the cholesterol moiety of LDL2 is perhaps derived from the liver while the protein and phospholipid portions may represent remnants of VLDL catabolism.(ABSTRACT TRUNCATED AT 400 WORDS)