The role of adipose tissue in glucose utilization in irradiated rats

The authors studied the conversion of U-14C-glucose to total lipids, fatty acids and glyceride glycerol in the epididymal adipose tissue of rats X-irradiated with a single whole body dose of 14.4 Gy X-rays. Analyses were carried out 1, 24, 48 and 72 h after irradiation. In the adipose tissue of irradiated rats, the incorporation of 14C-glucose into all the lipid fractions was raised throughout the whole time of observation (300-600% of the control value). Most of the 14C-glucose was incorporated into the glyceride glycerol fraction.     

Early effects of feeding excess vitamin A: mechanism of fatty liver production in rats

Oral administration of vitamin A (30,000 IU daily for 2 days) to young rats caused a marked increase in hepatic glycogen, cholesterol, and glycerides, while hepatic phospholipid content remained almost unaltered. In an examination of the pathogenesis of the lipid accumulation, it was found that more glucose-(14)C was incorporated into liver lipids in vitamin A-fed rats, whereas incorporation of glucose-(14)C and dl-glycine-(14)C into liver protein remained unaltered. The increase in glucose-(14)C incorporation was confined to the glyceride-glycerol portion of the lipids; incorporation into liver fatty acids was inhibited. Plasma free fatty acid concentrations were elevated. It is postulated that in the vitamin A-fed rats, increased accumulation of lipids in the liver is caused by a stimulation of fatty acid mobilization from adipose tissue and enhanced formation of glycerophosphate through glycolysis, with consequent increase in the glyceride synthesis in the liver. The weight of the adrenals was increased, whereas cholesterol concentration in the gland was decreased, after administration of vitamin A to rats. This indicates adrenocortical stimulation. Interestingly enough, vitamin A feeding did not affect either the level of liver lipids or of plasma FFA in adrenalectomized rats.     

Effects of fasting and refeeding on the in vitro insulin sensitivity of rat aorta

Rat aorta responds to refeeding after a fast in a manner similar to adopose tissue and liver by developing an enhanced capacity for lipogenesis and glycogen synthesis from glucose. The in vitro incorporation of D-U-14C-glucose into aortic triglycerides and glycogen was two- to four-fold higher in rats refed for three to five days after a three day fast than in ad libitum fed controls. Insulin significantly stimulated this incorporation only during refeeding for three days after a three-day fast. The glycogen synthesizing system appeared to be stimulated and to become sensitive to insulin earlier in the refeeding process than did the lipogenic system. The in vitro incorporation of 14C-glucose into aortic phospholipids was less affected by the nutritional state of the animal, and was not stimulated by insulin at any stage of the experiment. Possible mechanisms for the development of insulin supersensitivity and the implications for lipid accumulation in the artery wall are discussed.     

The effect of ionizing radiation on lipid metabolism in lymphoid cells

Lipid metabolism was studied in lymphoid tissues of rats after whole body irradiation with doses producing damage of different degrees to lymphoid cells (4-10 Gy). The content of free cholesterol, cholesterol esters, and total phospholipids was determined in peripheral blood lymphocytes and thymocytes 1-2 h after exposure. Simultaneously, the rate of in vitro incorporation of 2 14C-acetate into total lipids, phospholipids, and cholesterol of lymphoid cells was estimated. It was shown that exposure of rats to ionizing radiation caused activation of lipogenesis. Cholesterol synthesis was activated after a dose of 4 Gy and decreased with increasing dose.     

Lipogenesis and gluconeogenesis in the liver of irradiated rats

The incorporation of 14C from [U-14C] glucose and 3H from 3H2O into the total lipids fatty acids and glycogen of the liver incorporation of 3H from 3H2O into blood glucose was studied in rats totally irradiated in a dose of 14.4 Gy. It is shown that in the liver of irradiated rats glucose is accumulated in considerable amounts as glycogen but it is slightly used as a source of carbon for lipid synthesis. The study of 3H incorporation shows that irradiation stimulates glucogenesis, glyconeogenesis and lipogenesis in the liver.     

Effect of Bauhinia forficata extract in diabetic pregnant rats: maternal repercussions.

Bauhinia forficata, commonly known as "paw-of-cow", is widely used in Brazil folk medicine for the treatment of Diabetes mellitus. The purposes of present study were to determine the repercussions of diabetes on the defense system against oxidative stress in pregnant female rats and to characterize the influence of the treatment with Bauhinia forficata extract on the antioxidant system, glycemic control, hepatic glycogen, cholesterol, triglycerides, total proteins and lipids. Virgin female Wistar rats were injected with 40 mg/kg streptozotocin (STZ) before mating. Oral administration of an aqueous extract of Bauhinia forficata leaves was given to non-diabetic and diabetic pregnant rats in 3 doses: 500 mg/kg from 0 to 4th day of pregnancy, 600 mg/kg from 5th to 14th day and 1000 mg/kg from 15th to 20th day. All the females were killed on the day 21 of pregnancy. A maternal blood sample was collected by venous puncture and the maternal liver was removed for biochemical measurement. The diabetic pregnant rats presented hyperglycemia, hyperlipemia, hypertriglyceridemia, hypercholesterolemia, hyperuricemia, decreased determinations of reduced glutathione (GSH) and superoxide dismutase (SOD). Treatment with B. forficata extract did not interfere in the albumin, total protein and lipid, triglyceride, cholesterol and SOD determinations. Increased hepatic glycogen, decreased uric acid concentration and increased GSH activity was observed. This last fact suggests that the plant may have some action on antioxidant defense system. However, the demonstration of the active component present in B. forficata responsible for its antioxidant effect and the increase in hepatic glycogen deserve further investigation.     

Changes in Amino Acid Metabolism in vivo with Time after Feeding

Changes in the metabolism in vivo of amino acids with the lapse of time after feeding a diet were investigated by measuring the incorporation of ¹⁴C into some body components one hour after injection with ¹⁴C-amino acid mixture.

The incorporation of ¹⁴C into protein in the liver and carcass was rather constant, but that into blood sugar, liver glycogen, and lipids in the liver and carcass showed a change with the lapse of time after feeding a 25% casein diet or a protein-free diet. The incorporation of ¹⁴C into liver glycogen was stimulated shortly after feeding, but it was reduced at 7 hr, when a large amount of glycogen was still in the liver. On the contrary, the specific activity of blood sugar increased with the lapse of time after feeding. The conversion of ¹⁴C-amino acids into lipids in the liver and carcass was stimulated shortly after feeding.

The incorporation of ¹⁴C into protein was higher in the rats fed the protein-free diet than in those fed the 25% casein diet, and the higher incorporation was partly counterbalanced by the lower incorporation of ¹⁴C into lipids and glycogen in the rats fed the protein-free diet.     

The effect of hyperosmolarity on muscle glycogen accumulation.

Soleus (red) and extensor digitorum longus (white) muscles from Sprague Dawley rats were incubated with 6-14C-labelled glucose in normal and in hyperosmotic media. Hyperosmolarity decreased 6-14C-glucose incorporation into muscle glycogen in a dose dependent manner and increased glycolysis and glucose oxidation. Increased glycogenolysis rather than decreased glycogenesis was responsible for the reduction in labelled glycogen accumulation.     

Effect of aflatoxin B1 on lipids of rat tissues.

The effect of aflatoxin B1 on lipids of liver, kidney, adipose and plasma of rats was studied. A single dose administration (6 mg/kg body weight) increased liver and kidney weights and their total lipids within 24 h. Increase in liver lipids was confined mainly to phospholipid and cholesterol, whereas triglycerides showed a significant decrease. Adipose tissue triglycerides were, however, increased. Plasma showed decreases in triglycerides, free fatty acids and cholesterol. Incorporation studies with palmitate-1-14C revealed increased incorporation in adipose tissue lipids and decreased incorporation in liver and plasma lipids, thereby indicating an increased synthesis of lipids in adipose. Their mobilization to plasma was, however, inhibited, hence the low levels of triglyceride in liver. But the adrenals showed hypo-activity upon aflatoxin B1 administration.     

Glucose infused through the portal vein enhances liver gluconeogenesis and glycogenesis from [3-14C]pyruvate in the starved rat

After a pulse of [3-14C]pyruvate, 24 hr starved rats were infused through the portal vein with two different doses of glucose (7.8 or 20.8 mg/min) or the medium, and blood was collected from the inferior cava vein at the level of the suprahepatic veins. The highest dose of glucose enhanced the appearance of [14C]glucose in blood from the 2nd to the 20th min after tracer delivery. It also enhanced production of [14C]glycogen and concentration of glycogen in the liver after 5 and 20 min. At 20 min of glucose infusion the appearance of [14C]glyceride glycerol in liver as well as liver lactate concentration and lactate/pyruvate ratio were increased. The low dose of glucose used enhanced liver values of [14C]glycogen, [14C]glycogen specific activity and glycogen concentration. Our results support the hypothesis that in the starved rat glucose is converted into C3 units prior to being deposited as liver glycogen and based on the liver zonation model (Jungermann et al., 1983) it is proposed that glucose stimulated gluconeogenesis by shifting the liver to the cytosolic redox state as a secondary consequence of increased glycolytic activity.     

Lipogenesis and cholesterogenesis in the liver of rats after cholesterol loading

Intensity of fatty acids and separate classes of lipids synthesis was studied in vitro in the liver of white rats at loading by cholesterol in the dose of 300 mg/kg once a day during 30 days by incubation of organ homogenate with [6-(14)C] glucose, [2-(14)C] lysine, [1-(14)C] palmitic acid with following determination of radioactivity of fatty acids, phospholipids, cholesterol, acylglycerols radioactivity was investigated. The inhibition of fatty acids and separate classes of lipids synthesis in vitro in the liver of white rats at loading by cholesterol at the use of [6-(14)C] of glucose and [2-(14)C] lysine, as predecessors of fatty acids and lipids and stimulation of lipids synthesis at the use of [1-(14)C] palmitic acid as the predecessor was established. The loading of white rats by cholesterol results in its synthesis inhibition in the liver during incubation of its homogenates with [6-(14)C] glucose and does not influence the cholesterol synthesis during incubation of homogenates with [2-(14)C] lysine and [1-(14)C] palmitic acid. Thus synthesis of fatty acids and their use in the phospholipids and acylglycerols synthesis in the liver of white rats with hypercholesterolemia sharply decreases during incubation of their homogenates with [6-(14)C] glucose and [2-(14)C] lysine, and the synthesis of cholesterol, phospholipids and acylglycerols - increases during incubation with [1-(14)C] palmitic acid.     

Protection to glycolysis by a combination of 5-hydroxy-L-tryptophan and 2-aminoethylisothiuronium bromide hydrobromide in lethally irradiated rats.

Rate of glycolysis in vivo at different time intervals following 8 Gy [LD100(30)] whole body gamma radiation (WBGR) was evaluated by estimating liver glycogen, blood sugar, serum lactic dehydrogenase (LDH) and blood lactic acid concentration in adult male Sprague Dawley rats. Within 1 hr of radiation exposure, a significant fall in liver glycogen was observed in rats fed food and water ad libitum. The glycogen content increased after 24 hr and had returned to control level on 7th day after radiation exposure. Blood sugar, serum LDH and blood lactate levels increased significantly as compared to non irradiated controls. Pretreatment with 5-hydroxy-L-tryptophan (5-HTP; 100 mg/kg) + 2-aminoethylisothiuronium bromide hydrobromide (AET; 20 mg/kg) ip 30 min before 8 Gy WBGR, modified these values and restored them to normal level on 7th day post-irradiation.     

Effect of Retinol on Liver Lipid Metabolism of Rats

Effect of feeding 4.23, 16.94 and 27.53 mg of retinol daily for 10 days on the liver lipids of adult rats has been studied. Feeding of different amounts of retinol produced dose dependent toxicity symptoms in rats. Retinol feeding resulted in significant elevations of liver total lipids, total fatty acids, and glycerides, The amounts of liver esterified cholesterol were significantly raised in rats fed different amounts of retinol. Acetate-1-¹⁴C incorporation was increased in liver total cholesterol of rats fed 27.53 mg retinol and in free cholesterol of all retinol fed rats. Total ¹⁴C activity of hepatic triglycerides of retinol fed rats was the same as that of control, but their specific activity was decreased. Significant alterations were noted in phosphatidyl serine, lysophosphatidyl choline, lysophosphatidyl ethanolamine, sphingomyelin, phosphatidyl choline, phosphatidyl ethanolamine and phosphatidic acid and polyglycerophosphate fractions in liver rats fed different amounts of retinol.     

Synthesis of lipids in the thymus of irradiated rats

Changes in the synthesis of total lipids from 14C-glucose and 3H2O and in triacylglycerol concentration in the thymus of rats X-irradiated with a single dose of 14.35 or 6.0 Gy were investigated. Both lipid synthesis and TAG concentration were found to increase in the irradiated rat thymus.     

Synthesis of lipids in the thymocytes of irradiated rats

During the first two hours following whole-body gamma-irradiation of rats with a dose of 7.5 Gy, the content of free cholesterol, phosphatidylcholine and phosphatidylethanolamine in the thymus decreases. Incorporation of 2-14C-acetate into cholesterol and fatty acids of thymus phospholipids in vitro is inhibited. At a dose of 4 Gy, incorporation of 2-14C-acetate into cholesterol and total lipids of thymocytes is activated.     

Incorporation of acetate-1-14C into lipids by the perfused liver of normal, X-irradiated, or partially hepatectomized rats

In order to study lipid metabolism in the liver without interference due to transport from and to the liver the isolated livers of normal, X-irradiated, and partially hepatectomized rats were perfused with acetate-1-(14)C and the distribution of radioactivity in total lipids, total fatty acids, individual lipids, and fatty acids of individual lipids was determined. In X-irradiated animals, an increased incorporation of acetate into many lipids, particularly into cholesterol, was observed. Lipids in the liver of the partially hepatectomized rats exhibited a marked increase in triglyceride content together with a decreased rate of incorporation into all but the phospholipid fractions. It is concluded that the increase usually observed in lipid pontent of the regenerating liver is due to the changes in transcort rather than to changes in synthesis. The changes observed in irradiated liver could be the result of alterations in the metabolism of precursors common to most lipids.     

14C-metabolism during callus induction in tobacco

Tobacco pith-phloem explants and callus were incubated in ¹⁴C-glucose, ¹⁴C-acetate or ¹⁴C-bicarbonate on different days in culture in the dark. ¹⁴CO₂ production and ¹⁴C incorporation into ethanol-insoluble components were generally greater in the subcultured callus than in the pith-phloem explants during days 0 to 5 in culture. Greatest radioactivity from all substrates was in the ethanol-soluble portion, which was further fractionated into lipids, amino acids, sugars and organic acids. Although incorporation into the different fractions varied with the substrate, the patterns of labelling were relatively similar in the two tissues. The greater wound metabolism in the subcultured callus in comparison to the pith-phloem explant during the induction phase of callus formation was correlated with the earlier visible initiation of cell proliferation in the subcultured tissue.     

Quantitative regularities and peculiarities of the development of the cerebral form of radiation sickness at fractionated irradiation

Several peculiarities in manifestations of cerebral form of radiation sickness have been revealed at a fractionated double irradiation with equal and unequal doses per fraction and different intervals between the fractions. A reliable increase in average lifespan of rats irradiated with (100 + 100 Gy) equal doses at 10 and 60 min intervals between two fractions compared to the single radiation exposure to 200 Gy has been obtained. Lifespan of rats irradiated with a total dose greater than 200 Gy in most cases of double exposures with 10 min interval was reliably less than that for animals after a single exposure. The influence of the first dose on the reduction of animal average lifespan increased with fraction dose increasing from 150 to 300 Gy and was most pronounced at the total exposure dose of 400 Gy. Reaction of rats on the repeated irradiation was significantly weakened in comparison with the reaction on the first exposure. At a study of capacitation the interval of 30 min appeared to be more favorable compared to 10 min interval. Importance of a dose value in the first fraction has been demonstrated: the higher this value the worse the capacity of the rats 3 hours after the repeated exposure.     

Metabolism of radiolabelled chylomicron lipids in intact and hepatectomized rats

Intact rats removed more radiolabelled triacylglycerol, cholesterol, and cholesterol ester but not phosphatidylcholine (PC) in the first 6 min than hepatectomized rats. There was no difference between intact and hepatectomized rats in the transfer of radiolabelled chylomicron lipids to other lipoproteins. Specific radioactivity measurements demonstrated a net transfer of PC (intact and hepatectomized rats) and unesterified cholesterol (intact rats only) onto both the low density lipoprotein/high density lipoprotein-1 (LDL/HDL1) and HDL2 fractions. [3H]Fatty acids were rapidly incorporated into blood cell phospholipids and into HDL and LDL cholesterol esters of both intact and hepatectomized rats. Substantial rearrangements of [3H]palmitate occurred during lipid uptake by liver.     

The origin of lipid accumulated in liver lysosomes after administration of triton WR-1339

The origin of the lipids accumulated in liver lysosomes after administration of Triton WR-1339 was investigated. When Triton WR-1339 was injected into rats, serum triglyceride and cholesterol increased markedly. The highest content of triglyceride was observed in the second-day serum, from which very-low-density lipoprotein (VLDL) was isolated. The VLDL was administered to normal rats, then the light mitochondrial fraction of the liver at 24 h was centrifuged in a sucrose density gradient. The activities of lysosomal enzymes, acid phosphatase, N-acetyl-beta-D-glucosaminidase and acid lipase, were all shifted to less dense fractions as compared with those of normal lysosomes. [3H]Triglyceride-labeled VLDL was injected similarly, and at 12 and 24 h after the administration, the light mitochondrial fraction of the liver was fractionated by sucrose gradient centrifugation. Protein content and radioactivity in the immunoprecipitate with anti-VLDL serum at 12 h showed almost the same distribution as acid phosphatase activity. At 24 h, though acid phosphatase activity, immunoprecipitable protein content and radioactivity were all found in less dense fractions than in the case of normal lysosomes, the former two distributions were significantly different from the latter. The anti-VLDL serum reacted in Ouchterlony tests not only with Triton-induced VLDL and normal VLDL but also with the extract from low-density lysosomes. These results suggest that the lipids accumulated in low-density lysosomes following the administration of Triton WR-1339 were probably derived from the elevated serum VLDL induced by the treatment.