Stimulation of tumor growth in adult rats in vivo during an acute fast

These experiments investigate an increase in tumor growth that occurs in adult rats in vivo during an acute fast. The effects of feeding, fasting, and underfeeding on the growth of Morris hepatomas 5123C and 7288CTC in Buffalo rats and of Walker carcinoma 256 and Jensen sarcoma in Sprague-Dawley rats were studied. Animals were matched for tumor size and growth during a period of ad libitum feeding preceding the fasting or underfeeding. Tumor growth was documented by increased size and incorporation of [methyl-3H]thymidine into tumor DNA. Fasting increased the rate of growth of the tumors 3 to 4 times over that measured in fed rats. This effect began during the first day of fasting and ended abruptly on refeeding. After refeeding tumor growth slowed to the rate in fed rats. Tumors from fed or fasted rats were not different in cellularity or dry weight/g wet weight. A positive growth response in the tumor required lipolysis and ketosis in the host. No stimulation was observed during an acute fast in either immature rats or in mature rats whose weights had been reduced by underfeeding. These animals have small fat stores and show no increase in arterial blood free fatty acid or ketone body concentrations during an acute fast. Finally, underfeeding of adult rats raised the blood concentrations of these nutrients to values that were intermediate between those in fasted and fed rats. Tumor growth rates in these rats were intermediate between those in fasted and fed rats. The results support the proposal that an increase in availability of free fatty acids and/or ketone bodies is the stimulus that increases the rate of tumor growth during an acute fast.

Characterization of alterations in plasma lipoprotein lipid and apoprotein profiles accompanying hepatoma-induced hyperlipidemia in rats

Alterations in plasma lipoprotein lipid and apoprotein accompanying the hyperlipidemia of rats bearing Morris hepatoma 7288C were characterized. In tumor-bearing animals all plasma lipid classes except cholesterol ester (CE) were elevated, particularly free cholesterol (FC) and triglyceride (TG), which increased by 57 and 63%, respectively. Fasting only partially reduced the tumor-induced hyperlipidemia and had no effect on the ratios of FC/CE and TG/CE. Analysis of plasma lipoproteins revealed an elevation of VLDL, IDL, and LDL in host rats, with more than a 2-fold increase in both lipid and protein of VLDL. In contrast, the three high density fractions, HDL2, HDL3, and d greater than 1.21 g/ml, were reduced. The inverse changes in concentration of host lipoproteins of lower versus higher density indicate a defective catabolism of TG-rich lipoprotein. This possibility is supported by the analysis of apolipoprotein. The percentage of total apoprotein contributed by apo C-I and C-II was reduced in all host fractions except HDL2, while the C-IIIs remained unchanged except for a small decrease in C-III-3 of host VLDL and a slight increase in the combined C-IIIs of HDL2. These changes were reflected in the decreased C-I+C-II/C-III ratios of all host lipoprotein fractions. Apo E levels remained similar to control values except for a significant decrease in HDL2. Host VLDL showed increased apo A-IV and A-I content, while A-IV was decreased in HDL2. Changes in apo B profiles were also observed.

Characterization of sialyltransferases from serum of normal and hepatoma Mc-29 bearing chickens

Sialyltransferase was measured in serum of normal and hepatoma Mc-29 bearing chickens. By preparative isoelectric focusing the multiple forms of sialyltransferase from both kind of serums was studied as well. By using influenza virus neuraminidase an attempt was made for partial structural characterization of the sialylation sites in asialofetuin applied as exogenous acceptor for sialyltransferase determination. It was established an elevated serum sialyltransferase activity in tumor bearing chickens with tumor an enzyme form was detected with pI-4.99 identical with an enzyme form described previously in solubilized plasma membrane preparations from hepatoma Mc-29. Monitoring of multiple forms of serum glycosyltransferases may be of value in answering the problem concerning the tissue origin of serum enzymes.

Effect of KCD-232, a new hypolipidemic agent, on serum lipoprotein changes in hepatoma-bearing rats

Changes in serum lipoprotein profiles were characterized in Donryu rats subcutaneously implanted with an ascites hepatoma line of AH109A cells and the effect of a new hypolipidemic agent with a structure of 4-(4'-chlorobenzyloxy)benzyl nicotinate (KCD-232) was estimated. With the growth of hepatoma for periods of up to three weeks, a striking decrease in the high density lipoprotein (HDL) fraction and an enormous increase in the VLDL + LDL (very low density lipoprotein + low density lipoprotein) fraction were found in hepatoma-bearing rats when either precipitation method or electrophoresis was used. These lipoprotein profiles were not influenced by sex. Judging from the electrophoretogram, the increase in VLDL + LDL fraction was due mainly to an increase in VLDL fraction. The oral administration of KCD-232 significantly suppressed the hepatoma-induced increase in VLDL + LDL with little or no influence on the hepatoma-induced decrease in HDL. There existed a positive correlation between the hepatoma weight and (VLDL + LDL)-cholesterol concentration and a negative one between hepatoma and HDL-cholesterol.

Regulation of lactate production and utilization in rat tumors in vivo

These experiments were performed to determine the factor(s) that regulate lactic acid production and utilization by rat tumors in vivo. Arteriovenous differences for glucose and lactic, pyruvic, 3-OH-butyric, and acetoacetic acids were measured across "tissue-isolated" Walker 256 sarcocarcinomas and Morris 5123C hepatomas in fasted rats anesthetized with sodium pentobarbital. Twenty-six per cent of the sarcocarcinomas (n = 53) and 48% of the hepatomas (n = 29) utilized blood lactic acid. The remainder released lactic acid into the venous blood. The steady-state rate of glucose consumption was similar in both lactate-producing and lactate-utilizing tumors. The range of lactate concentrations in the blood leaving the tumors was narrower than the range of lactate concentrations in the blood entering the tumors. This difference was caused by tumor lactic acid production at low arterial lactate concentrations and tumor lactic acid utilization at high arterial lactate concentrations. Individual tumors changed from lactic acid production to lactic acid utilization in a matter of minutes in response to an increase in the arterial lactic acid concentration. Mean lactic plus pyruvic acid concentrations and lactic/pyruvic acid ratios in the tumor venous blood were 2.15 +/- 0.22 and 23.4 +/- 3.7 mM, respectively, for Walker sarcocarcinoma 256 (n = 18) and 1.28 +/- 0.13 and 48.1 +/- 5.1 mM, respectively, for hepatoma 5123C (n = 11). The results suggest: that a steady-state lactic plus pyruvic acid concentration and lactic/pyruvic acid ratio are maintained in the tumor cell cytoplasm by the active glycolytic pathway and by lactic acid dehydrogenase; that the tumor intracellular concentrations equilibrate with the arterial blood and that the tumor steady state is expressed in the tumor venous blood; and that tumor lactic acid production or utilization results from the equilibration between the variable arterial lactic acid concentration and the more constant tumor intracellular steady-state lactic acid concentration. Since the arterial lactate concentration may be less than, greater than, or equal to the intracellular steady-state concentration, an individual tumor may produce, utilize or neither produce nor utilize lactic acid.

Characterization of murine hepatoma BW7756. III. Hematological profile of a tumor-associated anemia

A severe anemia develops in recipient C57L/J mice after syngeneic transplantation of the BW7756 murine hepatoma. The tumor undergoes an exponential growth spurt in the 14-21 days post-implantation, accompanied by a parallel increase in serum alpha-fetoprotein levels and a significant decrease of hemoglobin concentration and hematocrit extending to the 28th day. Concomitant with the decreased hematocrit, the blood volume displayed a 10% increase. The blood cell population was generally one of reticulocytosis and leukocytosis. Mild icteric plasma was observed and both "cold" and "warm" antibodies were detected in the sera of tumor-bearing mice. An elevation of IgM was observed by day 7, followed by a depletion of IgG1 and IgG2 throughout the tumor growth period. When RBCs of tumor-bearing mice were compared to those of normal mice, the same degree of osmotic fragility was found. However, the lifespan of the transfused RBC was shorter in tumor-bearing mice than in normal mice (half-life: 2 days vs. 4 days). The data suggest a type of auto-immune hemolytic anemia which is analogous to various hematopoietic disturbances described for murine hosts bearing solid tumors distal to hematopoietic sites.

[Inhibition of metastasis by anti-platelet agents-prostaglandins]

The role of platelets in the development of blood-borne metastasis is overviewed, referring to our own experimental data. Platelets interact with tumor cells in circulation or in capillary beds to form tumor thrombi which accelerate the lodging process of metastasis. This interaction is mediated by platelet aggregating substances, such as ADP, thrombin-forming substance and certain membrane proteins from tumor cells. The aggregation of platelets is followed by secretion of various growth factors including PDGF, EGF and TGF-beta although the implication of these factors in growth promotion of metastatic foci is presently uncertain. Certain antiplatelet agents, particularly prostacyclin and prostaglandin E1 inhibit pulmonary metastasis in animal models and thus appear to be potentially useful in the prophylaxis of metastasis.

Plasma proteinase inhibitors in Morris hepatoma-bearing rats: changes in the blood level and synthesis in tissue slices

The antiproteinase activities against trypsin, chymotrypsin, elastase, papain and rat leucocyte proteinases were determined in plasma from control and Morris hepatoma-bearing rats. Bovine trypsin and chymotrypsin were similarly inhibited by the two types of plasma whereas porcine pancreatic elastase, papain and rat leucocyte neutral proteinases were more efficiently inhibited by plasma from tumour-bearing rats. The increased plasma concentrations of some proteinase inhibitors, as determined by rocket immunoelectrophoresis, are suggested to be responsible for the observed differences in inhibition. The highest increases in plasma of tumour-bearing rats were observed for alpha 2-macroglobulin and alpha 1-acute-phase globulin. The synthesis and secretion of six proteinase inhibitors: antithrombin III, alpha 1-proteinase inhibitor, alpha 1-macroglobulin, alpha 2-macroglobulin, alpha 1-acute-phase globulin and haptoglobin, as well as albumin, were measured in tissue slices from rat liver and Morris hepatoma after incubation with [14C]leucine. Local inflammation inflicted upon the tumour-bearing rats increased formation of acute-phase proteins in liver slices but not in hepatoma slices.

Evaluation of a histologic classification of mouse liver tumors based on pyruvate kinase isozymes and status of host lipids

The histologic classification of mouse liver tumors, i.e., hepatic nodules type 1 and type 2 and hepatocellular carcinomas, was evaluated by a comparison of several biologic and biochemical markers that have been shown to be useful for the grading of tumor malignancy. The liver tumors were induced by N,N'-2,7-fluorenylenebisacetamide (CAS: 304-28-9; N,N'-fluoren-2,7-ylenebisacetamide) administration to male CD-1 mice. The ability to induce L-type pyruvate kinase activity in response to a high-carbohydrate diet disappeared in almost all the liver tumors. However, fairly good correlations were observed between the histologic classification and the relative weights of liver and intraperitoneal fat pads, between the histologic classification and the level of serum total cholesterol, and between the histologic classification and the K-type pyruvate kinase activity. The results suggest that the present histologic classification reflects the degree of tumor malignancy, and therefore, it would be useful for the classification of mouse liver tumors.

Changes in the cell membrane of erythrocytes in tumor-bearing rats

Cell electrophoresis of erythrocytes taken from AH 7974 hepatoma-bearing rats showed a marked decrease in the surface negative charge, as represented by a decrease in cell mobility. This change in the erythrocyte membrane began during the stationary phase of growth of transplanted tumor cells and became more pronounced in the late phase, during which time a marked decrease in the amount of sialidase-sensitive sialic acid present in the plasma membrane also took place. The erythrocytes of AH 7974F-bearing rats (which died from tumor growth much earlier than the AH 7974-bearing rats) had a similar, but less marked, decrease in their electrophoretic mobility and in the amount of sialidase-sensitive sialic acid present. These erythrocytes all had somewhat abnormal cell morphology, their shapes being slightly spherocytic.

Serum amino acid levels in patients with hepatocellular carcinoma

Serum amino acid concentrations in cirrhotic patients with and without hepatocellular carcinoma (HCC) were investigated. Elevation of serum aromatic amino acids (AAA) and methionine levels observed in cirrhotic patients without malignancy was not apparent in cirrhotic cases with HCC, and thus the ratio of branched chain amino acids (BCAA) to AAA was not so diminished in the latter cases. Development of hepatic encephalopathy in cirrhotic patients with HCC led to only a slight change in the serum aminogram characteristic of hepatic failure. In patients who underwent operations, tissue amino acid compositions of hepatocellular, gastric, and colon cancers were compared with each other and their respective surrounding epithelia. Amino acid contents in the tumor tissue were generally higher than those in the respective nontumorous parts, especially in the case of HCC. The methionine, tyrosine, and phenylalanine contents in HCC were much higher than in cirrhotic or normal liver. Serum aminograms in rats with ethionine-induced HCC were similar to those in cirrhotic patients with HCC. Amino acid contents in HCC were much higher than those in the surrounding cirrhotic liver tissue of rats. Serum and liver tyrosine and isoleucine contents rose significantly in rats 5 to 6 weeks after the initiation of a 0.25% ethionine-containing diet. After the 20th week of the experiment, by which time well-differentiated HCC had developed, liver tyrosine and isoleucine contents increased whereas serum isoleucine concentrations decreased. The results suggest that the serum amino acid patterns characteristic of cirrhotic patients with HCC may result from the increased consumption of amino acids by HCC. Determinations of the amino acid levels are also useful for estimating the prognosis and discovering imminent hepatic encephalopathy in cirrhotic patients with HCC.

Gossypol inhibits estrogen binding to rat alpha-fetoprotein

We find that gossypol, a male anti-fertility compound, is a reversible competitive inhibitor of estrogen binding to rat alpha-fetoprotein (AFP). The Kd of gossypol for rat AFP is 1.75 microM, which is similar to gossypol's affinity for lactate dehydrogenase isozyme X, the putative site where gossypol exerts its anti-fertility effects. Reacting sodium cyanoborohydride with gossypol reduces its affinity for AFP, showing that intact aldehyde groups on gossypol are important for binding to rat AFP and indicating that gossypol is specifically inter-acting with a nucleophilic site on AFP that influences estrogen binding.

Epoxide hydrolase: a marker for experimental hepatocarcinogenesis

Rat liver chemical hepatocarcinogenesis, induced by interrupted feeding of 2-acetylaminofluorene, results in various cellular preneoplastic stages and finally in a hepatoma in about 70 to 90 percent of the rats. The putative precursors of hepatomas, called hyperplastic nodules, appear after 12 weeks of feeding and, after 16 weeks of feeding carcinogen, most of them are persistent. Epoxide hydrolase is a tightly bound endoplasmic reticulum enzyme which is strongly induced in hyperplastic nodules and hepatomas. This enzyme has been purified, high-titre rabbit antiserum prepared to it, and this antiserum used to search for epoxide hydrolase immunodeterminants in the sera from chemically induced nodule or hepatoma bearing rats. An enzyme linked immunosorbent assay (ELISA) assay using this antiserum showed significant titres of circulating microsomal epoxide hydrolase antigen, range 0.01 to 2.50 (mean 1.18 +/- 0.30) micrograms per ml, in all 24 hepatoma bearing rats tested. Eight sera from animals with large hyperplastic nodules were also significantly positive for this antigen, while sera from six normal controls were negative (less than 0.004 microgram per ml serum). A passive hemagglutination inhibition assay with sheep or normal rat red blood cells sensitized with pure rat microsomal epoxide hydrolase was capable of detecting 0.2 microgram hydrolase per ml serum. With this assay, sera from four rats with hepatomas were found to contain 0.8 to 1.6 micrograms epoxide hydrolase immunodeterminants per ml. Control rat sera had no detectable immunodeterminants. Thus epoxide hydrolase, a marker induced during experimental chemical hepatocarcinogenesis and called the preneoplastic antigen, has been shown to be circulating in the tumor bearing host.

The effect of active immunization of rats with heterologous alpha-fetoprotein upon hepatocarcinogenesis induced by 3'-methyl-4-dimethylaminoazobenzene

Immunization of rats with a purified mouse alpha-fetoprotein (AFP) suspended in Freund's complete adjuvant resulted in the production of antibodies that could precipitate both mouse and rat AFPs. A group of rats was immunized first and then fed a diet containing 0.06% 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) for 10 weeks. In these rats the elevation of serum AFP as well as the development of hepatoma were markedly inhibited. Another group of rats was immunized after feeding the diet containing 3'-Me-DAB for 10 weeks. The development of hepatoma and production of serum AFP were also suppressed. In both groups the life span of the rats was prolonged by the immunization.

Efficacy of chemotherapeutic treatment of guinea pig hepatoma reflected in host's serum lipid composition

A correlation was found between the highly polar phospholipid (HPPL) content of serum lipids and the growth and metastasis of the line-10 hepatoma in strain 2 guinea pigs. Animals whose tumors were treated by intralesional injection of decarbazine (DTIC) or saline showed progressive tumor growth and metastasis resulting in death within 120 days of tumor implantation. The percent HPPl in the serum lipids of these animals rose to 40% by 80 days and remained elevated above 20-25% until death. Animals whose tumors were treated by intralesional injection of adriamycin were either cured of their tumors (67%) or showed little or no tumor growth. The percent HPPL in the serum lipids of these animals remained between 3 and 12% at all times. Adriamycin or DTIC injected into non-tumor-bearing animals resulted in an HPPL content of serum lipids that was not significantly different from that of control, saline-inoculated animals.

Alpha-fetoprotein dynamics during ethionine-induced hepatocarcinogenesis in rat

Rats fed on a diet containing 0.25% DL-ethionine (ethionine), which has been usually used as carcinogenic dose, demonstrated the early elevations of serum alpha-fetoprotein (AFP) approximately in week 6 of the feedings. After declining once between week 10 and 14, the serum AFP levels increased again in week 22 of the continuous feeding, when well differentiated hepatocellular carcinoma had already developed. The level of serum AFP after development of hepatoma was found to be lower than those seen during the early elevation of AFP. Furthermore, in ethionine-induced hepatoma-bearing rats, AFP levels in the tumors were rather low as compared to those in the nontumorous portions of the liver surrounding the tumors. The results indicated that ethionine-induced hepatocellular carcinoma is not an AFP-highly-producing tumor.

[Changes in the rhythms of the alpha-fetoprotein content of the blood serum of mice with hepatoma 22A and of tumor cell proliferation depending on the time of cyclophosphane administration]

A study was made of the content of alpha-fetoprotein (alpha-FP) in the blood serum and of proliferative processes in hepatoma 22A-bearing mice after injection of cyclophosphamide in a dose of 150 mg/kg at varying time of 4-day tumor growth. The data obtained indicate that the time of appearance of alpha-FP in the blood, the pattern of rhythmic fluctuations in protein content and in the number of DNA-synthesizing and mitotic cells of the tumor depend on the time of the cytostatic injection during the day. Besides, cyclophosphamide exerts a more powerful inhibitory effect on the content of alpha-FP in the blood serum and less powerful on the proliferative processes in hepatoma 22A.

The fatty acid levels of rat alpha-fetoprotein derived from fetuses, pregnancy and hepatoma sera

The fatty acid levels of alpha-fetoprotein (AFP) isolated from term rat fetuses is about half that of similar human preparations. Arachidonic and docosahexaenoic acids constitute about 33% of the total fatty acids in the rat AFP isolates. The AFP isolated from rat maternal and hepatoma sera have relatively low levels of these fatty acids. A comparison of the fatty acid contents of selected tissues from pregnant and non-pregnant rats does not show differences which might reflect the variable fatty acid levels of the fetal and maternal source AFP preparations.

Correlation of circulating levels of a serum protein with triiodothyronine levels and hepatoma growth

In this communication, we provide evidence that proliferation of transplantable Morris hepatoma 7777 might to some extent be regulated by triiodothyronine and/or a specific serum protein, the levels of which are correlated with levels of triiodothyronine. The protein has an estimated molecular weight of 80,000 and migrates as one band on polyacrylamide gel electrophoresis. In normal rats, this protein accounts for approximately 1% of the total serum protein. Both the circulating levels of the serum protein and proliferating of transplanted hepatoma cells were decreased in thyroidectomized rats. Elevated levels of the serum protein and increased cell proliferation were observed when animals had 70% of their lives removed prior to transplant, were given injections of triiodothyronine, or had a 10-day-old first transplant surgically removed. Some evidence is also provided suggesting that the synthesis of the serum protein is stimulated by thyroid hormone.

Purification of specific antibody to alpha-foetoprotein and its immunological effect on cancer cells

Human of rat alpha-foetoprotein (AFP) was highly purified from ascitic fluid or serum of hepatoma bearers. The purification was carried out mainly by means of immunoadsorbent chromatography using Sepharose coupled to specific anti-AFP antibody with BrCN activation, and by Sephadex gel filtration. Horses were immunized with the purified AFP and the specific antibody was isolated from the antiserum by means of an immunoadsorbent coupled to purified AFP. The specific antibody was found to bind specifically with AFP-producing tumour cells. The antibody was applied for radio immunodetection of the tumour. 125I-labelled antibody was administered to patients or rats with hepatoma, and radioactivity localized in the tumours was scintiscanned with a scintillation camera. In this way, the location of the tumour was detected in about 50% of the hepatoma bearers. The cytotoxicity of the antibody was clearly demonstrated both in vitro and in vivo in animal experiments. The antibody was administered to patients with advanced hepatoma. Although no improvement of the disease was demonstrated, serum AFP levels decreased greatly and in some cases low AFP levels were maintained for long periods suggesting that the antibody suppressed AFP-producing hepatoma cells. No significant side effects were observed in patients who had been administered with the horse antibody.

Regulation of urea cycle enzymes in transplantable hepatomas and in the livers of tumor-bearing rats and humans

The levels of the five enzymes of the urea cycle were measured in normal 5-week-old rats, in a transplantable hepatoma, and in the livers of tumor-bearing rats (host livers). The levels of all five enzymes were much lower in the hepatoma, although there was no exact correlation of the decrease in levels. In host livers, the levels were higher than in the tumors, but lower than in normal liver. The levels of all five urea cycle enzymes were positively correlated with dietary protein content in normal livers, in hepatomas, and in host livers. In fact, the hepatomas showed the greatest changes in response to diet. On all diets, the levels in host liver remained below those in normal liver, indicating that the decreased level was probably not due to preferential utilization of nutrients by the tumor. The levels of urea cycle enzymes in normal liver were not altered by a single injection of glucocorticoid, glucagon, or dibutyryl cyclic adenosine 3':5'-monophosphate. By contrast, in hepatoma, the levels were usually significantly elevated by the same treatment. In addition, the levels in host livers were always significantly elevated and were usually above those in normal animals, whether the latter were hormone treated or not. Injection of plasma from tumor-bearing rats into normal animals produced a decrease in the levels of all five enzymes; if glucagon was injected together with the plasma, large increases in levels were observed. This result supports the concept of a humoral factor produced by the tumor which affects the levels and the inducibility of urea cycle enzymes in host livers. Autopsied human primary hepatomas also showed levels of urea cycle enzymes below those in normal livers with host livers having intermediate values. A cell line derived from a human hepatoma showed induction of arginase by glucocorticoid in culture; in this, it resembled a cell line of the rat hepatoma. Tyrosine aminotransferase in human hepatoma cells was not induced by glucocorticoid; in this, it differed from the rat hepatoma cells where induction of this enzyme was observed.

Kinetics of the acute-phase reaction in rats after tumor transplantation

Transplantation of Yoshida sarcoma (solid type) and Zajdela ascites hepatoma tumors in rats induces a biphasic change in the concentration of the following five acute-phase proteins: alpha-1-acid glycoprotein; alpha-1-antitrypsin; haptoglobin; hemopexin; and ceruloplasmin. These proteins and other plasma proteins were quantitated by two-dimensional immunoelectrophoresis relative to normal serum concentrations. The elevation of most of these acute-phase proteins was greater in the second phase, during which serum levels increased continuously as the tumor burden increased until the animals died. The increase in haptoglobin concentration during the second phase was much higher in rats bearing Yoshida sarcoma than in rats bearing Zajdela tumors. Rats receiving irradiated tumor cells showed neither tumor growth nor second-phase protein changes. Significant increases in uptake of 3H-amino acids by isolated perfused livers of tumor-bearing rats provided evidence for an increase in the hepatic synthesis rates of the acute-phase proteins. Removal of the solid tumor resulted in a gradual decrease of acute-phase protein concentrations with concomitant increase in serum albumin concentration. These alterations in serum acute-phase proteins during tumor growth and after removal of the tumor may make their use attractive as biological markers of the response of the tumor-bearing animal to its tumor.

Increased histone acetylation and deacetylation in rat ascites hepatoma cells

Rates of histone acetylation and deacetylation in nuclei from fetal, adult, and two kinds of neoplastic rat hepatocytes were examined. Histone acetylation in isolated nuclei was measured in the presence of 6 mM sodium n-butyrate, a potent inhibitor of deacetylase, and in the absence of the inhibitor. The deacetylase activity was estimated from the difference between the rates with or without the inhibitor. Both histone acetylation and deacetylation in nuclei from hepatoma cells (AH 66 cells) occurred two times faster than those of nuclei from fetal and adult livers regardless of alpha-fetoprotein production. This increased acetylation and deacetylation in hepatoma cells may be ascribed to either the increased activities of the enzymes or the increased accessibility of histone to the enzymes in the chromatin. Autoradiographic analysis of acetylated histones showed that all of the internal histones of the nucleosomes were acetylated and that apparent difference was found in the pattern of acetylated fractions between hepatoma nuclei and normal liver cell nuclei.