Induction of liver lysosomal enzymes during the autophagic phase following phenobarbital treatment of rat

Phenobarbital was given to male rats as a single injection and as repetitive injections for 7 days. The effects of treatment on the lysosomal hydrolases acid phosphatase, cathepsin D, and aryl sulfatase were analyzed at different intervals ranging from 1 to 15 days after seven injections, and from 1 to 48 h after a single injection. In both cases, microsomal protein and NADPH-cytochrome c reductase were measured to ensure proper induction. After a single injection, a slight decrease in hydrolytic activities was observed. Repetitive administration of phenobarbital gave rise to a marked decrease of lysosomal enzyme activities 1 day after cessation of treatment. This decrease was followed by a continuous increase in activity up to day 3 and 4. One or 2 weeks after treatment, enzyme activities declined to control values. The increase in activity of lysosomal hydrolytic enzymes was correlated with the onset of induced autophagy of endoplasmic reticulum membranes described as occurring in liver upon cessation of phenobarbital exposure. It is concluded that phenobarbital treatment per se decreases lysosomal enzyme activities, whereas the induced autophagy following cessation of exposure is associated with enhanced levels of lysosomal hydrolases in rat liver.     

Absorption of 249Bk from the gastrointestinal tract of rats

In experiments with albino mongrel female rats a study was made of the absorption of 249Bk from the gastrointestinal tract after a single per os administration. The bulk of 249Bk (96 per cent) administered either intravenously or per os was mainly deposited in the skeleton and liver. The value of 249Bk absorption from the gastrointestinal tract by days 4 and 8 following administration was 0.05 per cent.     

The effect of the prophylactic use of benzonal on the cytochrome P-450 content of the liver in irradiated rats]

The rats (100 mg/kg, once a day, per os, during 3 days) were administered suspension of benzonal in starch gel before irradiation of 12 Gy. Induced and uninduced rats were irradiated on the following day after stopping benzonal administration and were decapitated at 10, 12, 15 and 21 o'clock during the first and second day after irradiation and also on the fourth day (day of mass death of irradiated rats). It has been established that irradiation changes the dynamics of cytochrome P-450 concentration in microsomal fraction of rat liver. The essential decrease of the content of cytochrome on the second day after irradiation was accompanied by intensification of the process of its inactivation, but stoichiometry between the decrease of P-450 and the increase of cytochrome P-420 was not observed. The high inducing and stabilizing effects of benzonal on cytochrome P-450 and on the liver persisted. In comparison with irradiation the unfavourable effect of benzonal on immunocompetent organs (thymus, spleen) was not found.     

The antioxidant effect of DL-alpha-lipoic acid on copper-induced acute hepatitis in Long-Evans Cinnamon (LEC) rats

The Long-Evans Cinnamon (LEC) rats, due to a genetic defect, accumulate excess copper (Cu) in the liver in a manner similar to patients with Wilson's disease and spontaneously develop acute hepatitis with severe jaundice. In this study we examined the protective effect of DL-alpha-Lipoic acid (LA) against acute hepatitis in LEC rats. LA was administered to LEC rats by gavage in doses of 10, 30 and 100 mg/kg five times per week, starting at 8-weeks-old and continuing till 12-weeks-old. Although LA had little effect against the increases in serum transaminase activities, it suppressed the loss of body weight and prevented severe jaundice in a dose-dependent manner. Antioxidant system analyses in liver showed that LA treatment significantly suppressed the inactivations of catalase and glutathione peroxidase, and the induction of heme oxygenase-1, an enzyme which is inducible under oxidative stress. Furthermore, LA showed dose-dependent suppressive effect against increase in nonheme iron contents of both cytosolic and crude mitochondrial fractions in a dose-dependent manner. Although at the highest dose, LA slightly suppressed the accumulation of Cu in crude mitochondrial fraction, it had no effect on the accumulation of Cu in cytosolic fraction. While LA completely suppressed the increase in lipid peroxidation (LPO) in the microsomal fraction at the highest dose, the suppressive effect against LPO in crude mitochondrial fractions was slight. From these results, it is concluded that LA has antioxidant effects at the molecular level against the development of Cu-induced hepatitis in LEC rats. Moreover, mitochondrial oxidative damage might be involved in the development of acute hepatitis in LEC rats.     

The antioxidant effect of DL-α-lipoic acid on copper-induced acute hepatitis in Long-Evans Cinnamon (LEC) rats

The Long-Evans Cinnamon (LEC) rats, due to a genetic defect, accumulate excess copper (Cu) in the liver in a manner similar to patients with Wilson's disease and spontaneously develop acute hepatitis with severe jaundice. In this study we examined the protective effect of DL-α-Lipoic acid (LA) against acute hepatitis in LEC rats. LA was administered to LEC rats by gavage in doses of 10, 30 and 100 mg/kg five times per week, starting at 8-weeks-old and continuing till 12-weeks-old. Although LA had little effect against the increases in serum transaminase activities, it suppressed the loss of body weight and prevented severe jaundice in a dose-dependent manner. Antioxidant system analyses in liver showed that LA treatment significantly suppressed the inactivations of catalase and glutathione peroxidase, and the induction of heme oxygenase-1, an enzyme which is inducible under oxidative stress. Furthermore, LA showed dose-dependent suppressive effect against increase in nonheme iron contents of both cytosolic and crude mitochondrial fractions in a dose-dependent manner. Although at the highest dose, LA slightly suppressed the accumulation of Cu in crude mitochondrial fraction, it had no effect on the accumulation of Cu in cytosolic fraction. While LA completely suppressed the increase in lipid peroxidation (LPO) in the microsomal fraction at the highest dose, the suppressive effect against LPO in crude mitochondrial fractions was slight. From these results, it is concluded that LA has antioxidant effects at the molecular level against the development of Cu-induced hepatitis in LEC rats. Moreover, mitochondrial oxidative damage might be involved in the development of acute hepatitis in LEC rats.     

Sodium selenite modulates tumour marker indices in N-nitrosodiethylamine-initiated and phenobarbital-promoted rat liver carcinogenesis

The effect of sodium selenite (Se) was investigated against two-stage rat liver carcinogenesis initiated by a single intraperitoneal injection of N-nitrosodiethylamine (DEN, 200 mg kg(-1) i.p.) followed by promotion with phenobarbital (PB, 0.05%) in a basal diet. Se (4 p.p.m.) was administered per os daily throughout the entire experiment, before the initiation, or during the promotion stage. The plasma, liver (hepatoma and surrounding tissue) and kidney tissue were investigated biochemically for lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and 5'-nucleotidase. These enzyme activities were increased (p < 0.001) in plasma of hepatoma-bearing rats compared with normal control rats. The elevation of these enzyme activities in plasma was indicative of the persistent deteriorating effect of DEN in cancer-bearing animals. Aminotransferase levels were decreased in hepatoma and surrounding liver tissue, whereas lactate dehydrogenase, alkaline phosphatase and 5'-nucleotidase were increased in the cancer condition. These enzyme activities were reversed to near normal control values in animals treated with Se. It is apparent that the beneficial effect of Se is primarily exerted on the initiation phase and secondarily during the promotion stage of DEN-initiated rat liver carcinogenesis. The analysis of marker enzyme activities taken together with our previous findings clearly indicates the antitumour efficacy of sodium selenite on DEN-induced hepatoma animals.     

Effect of triton WR-1339 on peroxisomal enzymes of rat liver

The effect of Triton WR-1339 on peroxisomal enzymes of rat liver was studied. The dose vs. response relationships of peroxisomal enzyme activities to Triton WR-1339 were first examined 3.5 days after injection. Catalase activity was reduced to 50% of that of the control at a dose of 200 mg per 100 g body weight; it was found that the decrease depended on the dose of this compound. Urate oxidase activity was not significantly affected. D-Amino acid oxidase activity showed intermediate behavior. The activities of these enzymes were found to be reduced more markedly at 2 days than at 3.5 days after injection, and subsequently the levels of the activities recovered. At 2 days after injection of a dose of 200 mg per 100 g body weight, the activities of catalase, D-amino acid oxidase and urate oxidase had decreased to 40, 60 and 60%,respectively, of the control values.It was found that the decreases in the activities of these enzymes caused by Triton WR-1339 had occurred in the large granule fraction, but not in the cytoplasm.Measurement of the specific activity, Ouchterlony gel diffusion and quantitative immunoprecipitation suggested that there was a similarity between the Triton WR-1339-treated and untreated rats in the nature of purified catalases.These results suggest that Triton WR-1339 depresses the activities of liver peroxisomal enzymes, especially the catalase activity.     

The influence of phenobarbitone on maternal and perinatal hepatic drug-metabolizing enzymes in the rat.

Phenobarbitone (PB) (75 mg/kg) was administered orally for three consecutive days to pregnant or lactating rats at different pre- and postnatal stages in order that the perinatal animals would receive the agent either by transplacental passage or via the milk. Control animals received equivalent volumes of saline. The dams, fetuses, and pups were killed 24 h after the last dose. Hepatic p-nitroanisole O-demetnylase (OD), carboxylesterase (CE), and bromosulfophthalein-glutathione (BSP-GSH) conjugating enzyme activities in a 12 100 g - 20 min supernatant of a 20% w/v homogenate were measured. The morphology of the developing rat liver in the absence and presence of PB was examined by electron microscopy. The results demonstrated that the transplacental passage of PB to rat fetuses at term or 3 days prepartum had no effect on either the hepatic drug-metabolizing enzyme activities or on the ultrastructural appearance of the liver. Increased hepatic OD activity was observed in the pregnant animal but no effect was observed in the lactating dam. Phenobarbitone received by the suckling rat had two distinct effects. Compared to control activities, twofold increases in hepatic OD activity were observed in rat pups as early as 4 days after birth, associated with a marked proliferation in hepatic smooth endoplasmic reticulum. In contrast, PB-related significant increases in neonatal hepatic CE and BSP-GSH conjugating enzyme activities were not observed until 21 days of age. In the 4-day-old treated pups, characteristic morphological changes included numerous small membrane whorls in addition to increased smooth endoplasmic reticulum and microbodies in the liver.     

Triacylglycerol metabolism in the phenobarbital-treated rat

1. Various aspects of triacylglycerol metabolism were compared in rats given phenobarbital at a dose of 100mg/kg body wt. per day by intraperitoneal injection; controls were injected with an equal volume of 0.15m-NaCl by the same route. Animals were killed after 5 days of treatment. 2. Rats injected with phenobarbital demonstrated increased liver weight, and increased microsomal protein per g of liver. Other evidence of microsomal enzyme induction was provided by increased activity of aminopyrine N-demethylase and cytochrome P-450 content. Increased hepatic activity of γ-glutamyltransferase (EC 2.3.2.2) occurred in male rats, but not in females, and was not accompanied by any detectable change in the activity of this enzyme in serum. 3. Phenobarbital treatment increased the hepatic content of triacylglycerol after 5 days in starved male and female rats, as well as in non-starved male rats; non-starved females were not tested in this regard. At 5 days after withdrawal of the drug, there was no difference in hepatic triacylglycerol content or in hepatic functions of microsomal enzyme induction between the treated and control rats. 4. After 5 days, phenobarbital increased the synthesis in vitro of glycerolipids in cell-free liver fractions fortified with optimal concentrations of substrates and co-substrates when results were expressed per whole liver. The drug caused a significant increment in the activity of hepatic diacylglycerol acyltransferase (EC 2.3.1.20), but did not affect the activity per liver of phosphatidate phosphohydrolase (EC 3.1.3.4) in cytosolic or washed microsomal fractions. A remarkable sex-dependent difference was observed for this latter enzyme. In female rats, the activity of the microsomal enzyme per liver was 10-fold greater than that of the cytosolic enzyme, whereas in males, the activities of phosphohydrolases per liver from both subcellular fractions were similar. 5. The phenobarbital-mediated increase in hepatic triacylglycerol content could not be explained by a decrease in the hepatic triacylglycerol secretion rate as measured by the Triton WR1339 technique. Since the hepatic triacylglycerol showed significant correlation with microsomal enzyme induction functions, with hepatic glycerolipid synthesis in vitro and with diacylglycerol acyltransferase activity, it is likely to be due to enhanced triacylglycerol synthesis consequent on hepatic microsomal enzyme induction. 6. In contrast with rabbits and guinea pigs, rats injected with phenobarbital showed a decrease in serum triacylglycerol concentration in the starved state; this decrease persisted for up to 5 days after drug administration stopped, and did not occur in non-starved animals. It seems to be independent of the microsomal enzyme-inducing properties of the drug, and may be due to the action of phenobarbital at an extrahepatic site.     

Placental transfer of halogenated benzenes (pentachloro-, pentachloronitro-, and hexabromo-) in rats.

The present study was carried out to provide information on the placental transfer of three organohalogens of environmental concern. Pentachloro-, pentachloronitro-, and hexabromobenzene were administered per os to rats daily on days 6 through 15 of gestation at level of 40, 100, and 200 mg/kg body weight. On day 22, the dams were killed and fetuses removed by caesarean section. Maternal brain, heart, kidney, liver, spleen and adipose tissue as well as whole fetus, fetal liver and fetal brain were analyzed for organohalogen residue by GLC. Pentachlorobenzene accumulated in the fetus to a greater extent than hexabromobenzene. In maternal tissues pentachlorobenzene accumulated to the greatest extent in adipose tissue, followed by liver, spleen, brain, heart and kidney. With hexabromobenzene, the greatest accumulation was observed in adipose tissue, followed by spleen, liver, heart, kidney and brain. Pentachloronitrobenzene was not detected (0.05 p.p.m.) in any maternal or fetal tissue.     

Dehydroepiandrosterone protects tissues of streptozotocin-treated rats against oxidative stress

Chronic hyperglycemia in diabetes determines the overproduction of free radicals, and evidence is increasing that these contribute to the development of diabetic complications. It has recently been reported that dehydroepiandrosterone possesses antioxidant properties; this study evaluates whether, administered daily for three weeks per os, it may provide antioxidant protection in tissues of rats with streptozotocin-induced diabetes. Lipid peroxidation was evaluated on liver, brain and kidney homogenates from diabetic animals, measuring both steady-state concentrations of thiobarbituric acid reactive substances and fluorescent chromolipids. Hyperglycemic rats had higher thiobarbituric acid reactive substances formation and fluorescent chromolipids levels than controls. Dehydroepiandrosterone-treatment (4 mg/day for 3 weeks) protected tissues against lipid peroxidation: liver, kidney and brain homogenates from dehydroepiandrosterone-treated animals showed a significant decrease of both thiobarbituric acid reactive substances and fluorescent chromolipids formation. The effect of dehydroepiandrosterone on the cellular antioxidant defenses was also investigated, as impaired antioxidant enzyme activities were considered proof of oxygen-dependent toxicity. In kidney and liver homogenates, dehydroepiandrosterone treatment restored to near-control values the cytosolic level of reduced glutathione, as well as the enzymatic activities of superoxide-dismutase, glutathione-peroxidase, catalase. In the brain, only an increase of catalase activity was evident (p < .05), which reverted with dehydroepiandrosterone treatment. The results demonstrate that DHEA treatment clearly reduces oxidative stress products in the tissues of streptozotocin-treated rats.     

Effects of Bacillus thuringiensis toxin on hepatic lipid peroxidation and free-radical scavengers in rats given alpha-tocopherol or acetylsalicylate

The effect of Dipel (D), a Bacillus thuringiensis-based bioinsecticide, on hepatic antioxidant enzyme activities and lipid peroxidation in rat liver was investigated. Administration of D in a dose of 1 mg/100 g body mass for 4 successive days increased the activities of glutathione peroxidase (GPx), glutathione reductase (GR) and the level of malondialdehyde (MDA) in rat hepatocytes. The activity of superoxide dismutase (SOD) and glutathione (GSH) level were decreased. Administration of D in rats pretreated with alpha-tocopherol (alphaT) or acetylsalicylic acid (ASA) decreased the activities of GPx, GR and MDA levels, while the GSH level was increased compared with rats treated with D alone. The SOD activity was increased in rats pretreated with alphaT before D, but decreased on pretreatment with ASA, compared with rats treated with D alone. The results indicated that D induced oxidative stress in rat liver that has been protected by prior administration of alphaT or ASA.     

Precocious alteration of digestive enzyme activities in small intestine and pancreas by chronic oral administration of protease inhibitor in suckling rats.

1. The role of endogenous CCK in the development of digestive enzyme activities in small intestine and pancreas was investigated in suckling rats. Synthetic protease inhibitor (camostat 100 micrograms/g bwt) was orally administered twice daily for 5 days from 11 days of age. 2. Pancreatic hypertrophy and hyperplasia, and alteration of pancreatic enzyme composition, especially decreases in amylase activity and increases in trypsin and chymotrypsin activities were produced by camostat treatment. These changes were completely suppressed by simultaneous administration of the potent CCK receptor antagonist L-364,718 (1 microgram/g bwt). 3. With camostat treatment, intestinal lactase activity decreased to 41%, while maltase and sucrase activities increased 3 and 2.5 times respectively. These changes in enzyme activities were not affected by the application of L-364,718. 4. The mucosal disaccharidase and pancreatic enzyme activities could not be modified by chronic subcutaneous injection of camostat. The precocious induction of maltase and sucrase activities by camostat treatment was also observed in the adrenalectomized pups. 5. These results indicate that pancreatic growth accompanied by alteration of digestive enzyme composition in the suckling rats is regulated by endogenous CCK, but the precocious induction of disaccharidase activities is not mediated by endogenous CCK released by camostat treatment.     

Characteristics of dehydroepiandrosterone as a peroxisome proliferator.

Treatment of rats with dehydroepiandrosterone (300 mg/kg body weight, per os, 14 days) caused a remarkable increase in the number of peroxisomes and peroxisomal beta-oxidation activity in the liver. The activities of carnitine acetyltransferase, microsomal laurate 12-hydroxylation, cytosolic palmitoyl-CoA hydrolase, malic enzyme and some other enzymes were also increased. The increases in these enzyme activities were all greater in male rats than in female rats. Immunoblot analysis revealed remarkable induction of acyl-CoA oxidase and enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme in the liver and to a smaller extent in the kidney, whereas no significant induction of these enzymes was found in the heart. The increase in the hepatic peroxisomal beta-oxidation activity reached a maximal level at day 5 of the treatment of dehydroepiandrosterone and the increased activity rapidly returned to the normal level on discontinuation of the treatment. The increase in the activity was also dose-dependent, which was saturable at a dose of more than 200 mg/kg body weight. All these features in enzyme induction caused by dehydroepiandrosterone correlate well with those observed in the treatment of clofibric acid, a peroxisome proliferator. Co-treatment of dehydroepiandrosterone and clofibric acid showed no synergism in the enhancement of peroxisomal beta-oxidation activity, suggesting the involvement of a common process in the mechanism by which these compounds induce the enzymes. These results indicate that dehydroepiandrosterone is a typical peroxisome proliferator. Since dehydroepiandrosterone is a naturally occurring C19 steroid in mammals, the structure of which is novel compared with those of peroxisome proliferators known so far, this compound could provide particular information in the understanding of the mechanisms underlying the induction of peroxisome proliferation.     

Effect of portacaval anastomosis on the activities of hepatic enzymes related to cholesterol and bile acid metabolism in rats.

1. The effect of a portacaval anastomosis on the activities of hepatic enzymes related to cholesterol metabolism was investigated in rats. 2. Portacaval anastomosis led to a fall in body weight and liver weight/body weight ratio, and to a rise in the activities of hydroxymethylglutaryl-CoA reductase and cholesterol 7alpha-hydroxylase per g of liver. The net effect was to maintain a normal activity of both enzymes per 100 g of rat. Diurnal rhythm in the activities of both enzymes was maintained after portacaval anastomosis. 3. The rate of excretion of total bile acids, per 100 g of rat, in bile fistula rats was not significantly decreased by portacaval anastomosis.     

Effect of somatotropin on the activity of mitochondrial alpha-glycerophosphate dehydrogenase in the liver of rats with hypo- and hyperthyroidism

The activity of mitochondrial alpha-glycerophosphate dehydrogenase in the liver of rats with hypothyrosis (two weeks after total thyroidectomy) is 36% of the normal level; in rats with hyperthyrosis (three weeks after subcutaneous implantation 2 mg of l-thyroxin on a kaolin base) it is 7.4 times as high. Bovine somatotropin (0.5 mg per 100 g of body mass) injected subcutaneously for 10 days has no effect on the enzyme activity in intact rats and in rats with hypothyrosis. In animals with hyperthyrosis somatotropin produces a 37% decrease in the enhance activity of the enzyme. Somatotropin fully normalizes a 25% increased amount of protein in the liver mitochondrial fractions of rats with hyperthyrosis.     

Inhibition of carbamoyl phosphate synthetase-I by dietary dehydroepiandrosterone.

Dehydroepiandrosterone (DHEA), administered per os, serves to prevent or retard the development of a variety of genetic and induced disorders in mice and rats. This treatment also results in the development of hepatomegaly, a change of liver color from pink to mahogany, peroxisome proliferation in hepatocytes and alterations in hepatocyte mitochondria morphology and respiration. We used one- and two-dimensional polyacrylamide gel electrophoresis (PAGE) to identify changes in the relative levels of liver proteins produced by DHEA treatment of rodents. In mouse liver, there were apparent increases in the levels of 26 proteins and decreases in the levels of 7 proteins. Of the induced proteins the most prominent had Mr approximately 72 K; this protein was identified in a previous study as enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase. Another protein of Mr approximately 28 K, of unknown nature, also was induced markedly by DHEA treatment of mice and rats. A protein of Mr approximately 160 K, which was identified as carbamoyl phosphate synthetase-I (CPS-I), was decreased markedly by DHEA action. This enzyme, which comprises approx. 15-20% of mitochondrial matrix protein, is involved in the entry and rate-limiting step of the urea cycle. The specific activity of CPS-I also was significantly decreased by DHEA, but serum urea levels were normal. To determine whether steroids other than DHEA also induced similar changes, mice were treated with various steroids for 14 days and, thereafter, liver proteins were evaluated by SDS-PAGE: estradiol-17 beta and isoandrosterone induced both the approximately 72 and approximately 28 kDa proteins, testosterone and androsterone induced the 28 kDa protein only, but etiocholanolone, pregnenolone and progesterone were without effect. The findings of this study serve to demonstrate that: (i) hepatic protein levels are affected by DHEA treatment of mice and rats; (ii) liver CPS-I activity is decreased significantly by DHEA treatment, but serum urea levels remain within the normal range; and (iii) sex steroids and some of their precursors, when administered per os, also alter liver protein levels.     

Organ and intracellular localization of short-chain acyl-CoA synthetases in rat and guinea-pig.

1. Homogenates of rat epididymal fat pad, heart, kidney, lactating mammary gland, liver, skeletal muscle and small intestinal mucosa have been partitioned into a particulate and supernatant fraction. With reliable marker enzymes for the mitochondrial matrix and the cytosol: propionyl-CoA carboxylase and pyruvate kinase, the distributions of the acyl-CoA synthetase activities measured at 1 and 10 mM C2, C3 and C4 over mitochondria and cytosol have been calculated. From these values an estimate was made of the K0.5 of the fatty acids. 2. A distinct fatty acid-activating enzyme was assumed to be present in one of the compartments when that fatty acid was activated with a K0.5 less than or equal to 1.5 mM in an amount of greater than 13% of the total cellular activity. Adipose tissue, gut, liver and mammary gland, all organs of a high lipogenetic capacity, contained a cytosolic acetyl-CoA synthetase. At 1 mM acetate 60, 31, 77 and 83% of the total cellular activities in these organs were cytosolic in nature, with activities of 0.021, 0.32, 0.37 and 1.16 mumol C2 activated per min per g wet weight, respectively. 3. Mitochondrial acetyl-CoA and butyryl-CoA synthetases were found in adipose tissue, gut, heart, kidney, mammary gland and muscle. They were absent in liver. Adipose tissue and liver contained a mitochondrial propionyl-CoA synthetase with activities at 1 mM C3 of 0.014 and 1.50 mumol C3 activated per min per g wet weight, respectively. 4. At 1 mM, C2 was activated with decreasing rates by kidney, heart, mammary gland and gut (7.6-1.0 mumol C2 activated per min per g wet weight). C3 (1 mM) activation was about equal (1.6-1.9 mumol C3 activated per min per g wet weight) in liver, kidney and heart. C4 (1 mM) was activated with decreasing rates by heart, liver, kidney and gut (4.0-0.5 mumol C4 activated per min per g wet weight) in the order given. 5. The influence of the isolation method and the diet on fatty acid activation in small intestinal mucosal scrapings have been studied. To demonstrate the existence of cytosolic acetyl-CoA synthetase in fed animals a pre-treatment of everted intestine by low amplitude vibration has been found essential. Also C16 activation was highly (95%) decreased in a non-pre-vibrated preparation. 24 h starvation lowered cytosolic C2 and total C16 activation by 90 and 80%, respectively. Refeeding of starved rats with a balanced fat-free diet, and not with sucrose only, gave the same cytosolic C2 and total C16 activation as normally fed rats. 6. In guienea-pig heart, kidney, liver and muscle about the same partitions have been found as in the respective rat organs. The acetate activation in liver was factor 6 lower. Acetate and butyrate activation in guinea-pig muscle was much higher (6 and 37 times, respectively).     

Metabolic effects of 3,5-dimethyl-3'-isopropyl-L-thyronine and 3,5,3'-triiodo-L-thyronine in the brain and liver of hypothyroid rats. Similarities and differences

The metabolic effects of 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT) on subcellular activities in brain and liver, have been compared to those of T3. Thyroidectomized hypothyroid rats were treated for 10 days with DIMIT (8 micrograms/100 g/day) or T3 (0.25 microgram/100 g/day). In liver mitochondrial oxidative phosphorylation, succinate cytochrome c reductase activities and nuclear RNA polymerases I and II activities were restored to normal level by DIMIT as well as by T3 treatment. In brain T3 treatment normalized both nuclear and mitochondrial activities. On the other hand daily injection of DIMIT restored like T3 nuclear activities whereas that of brain mitochondria were unaffected. We have also examined the early effects of a single injection of T3 (2.5 micrograms/100 g) or DIMIT (80 micrograms/100 g), 20 minutes prior sacrifice. DIMIT is as active as T3 in stimulation of oxidative phosphorylation and succinate cytochrome c reductase activity in liver mitochondria. However DIMIT treatment does not affect the properties of brain mitochondria. On the basis of these observations, it is suggested that there is a tissue specificity of mitochondrial receptors to DIMIT administration as it was shown at the nuclear level.     

Changes in the activity of enzymes,participating in glycogen metabolism of alloxan diabetic rats

Summary Alloxan diabetes induced in white rats by intraperitoneal injection of Aloxan-monohydrate (15 mg/100 g body weight) was used to study changes in the glycogen phosphorylase a and b, phosphoprotein phosphatases and hexokinase activities under insulin deficiency conditions. Among the enzymes studied, an increase in muscle phosphorylase a activity as well as the a/b ratio have been obtained. In diabetic muscle phosphoprotein phosphatases and hexokinase activities were diminished.AMP increased the liver glycogen phosphorylase activity twice in diabetic rats whereas in normal animals the enzyme was less sensitive to this effector. The changes in liver hexokinase activity at diabetes were not connected and correlated with the altered phosphorylase and protein phosphatase activities.The logical chain of probable molecular events taking place in muscle glycogen metabolism under the conditions of insulin deficiency is offered.