Chicken hepatic metabolism in vitro. Protein and energy relations in the broiler chicken--VI. Effect of dietary protein and energy restrictions on in vitro carbohydrate and lipid metabolism and metabolic hormone profiles

1. Ross male broiler chicks growing from 14 to 28 days of age were fed 14 and 20% protein diets (4 kcal day-1/body wt0.66) or 20 and 28% protein diets (2.8 kcal day-1/body wt0.66) in a 2 x 2 factorial arrangement to determine the effects of protein and energy intakes on in vitro lipogenesis (IVL) and net glucose production (NGP). Plasma concentrations of insulin, glucagon, thyroid hormones (T3 and T4) and somatomedin-C (Sm-C) were estimated by radioimmunoassay. 2. There was a significant (P less than 0.05) decrease in IVL in the chicks given the higher daily protein intake. 3. The higher protein intake increased (P less than 0.05) NGP while the lower energy intake decreased (P less than 0.05) NGP. 4. Insulin, both thyroid hormones and Sm-C were affected by dietary energy and protein intakes.     

Elevated insulin/glucagon ratios and decreased cyclic AMP levels accompany the glycogen and triglyceride storage syndrome in the hypothyroid chick

The role of endogenous glucagon and insulin on the hepatic glycogen and triglyceride storage syndrome in propylthiouracil (PTU)-induced hypothyroidism was investigated in the chick. PTU feeding in the diet resulted in a progressive increase in liver glycogen concentration associated with a concomitant decrease in hepatic glucose-6-phosphatase (G-6-Pase) activity. Plasma glucagon level was significantly decreased and insulin significantly increased after two days of PTU administration. These enzyme and hormone changes were associated with a significant increase in hepatic glucose-6-phosphate (G-6-P) and a decrease in cyclic AMP levels. Although our results do not directly prove, the data does suggest that the hepatic glycogen storage syndrome observed in the PTU-induced hypothyroidism in the chick is mediated through changes in pancreatic glucagon and insulin secretion. The extent of glycogen accumulation was inversely related to G-6-Pase which is a rate limiting glycogenolytic enzyme. A significant increase in the plasma insulin/glucagon ratio, along with a significant decrease in the hepatic cyclic AMP concentration, could most likely also account for the excessive hepatic triglyceride accumulation in the PTU-treated chicks.     

Methimazole, thyroid hormone replacement, and lipogenic enzyme gene expression in broilers

The purpose of this experiment was to determine the possible relationship between certain indices of lipid metabolism and specific gene expression in chickens fed methimazole to simulate hypothyroidism. Male broiler chickens (Gallus gallus) growing from 7 to 28 days of age were fed diets containing 18% crude protein and either 0 or 1 g methimazole per kilogram of diet. At 28 days, these two groups were further subdivided into groups receiving 18% crude protein diets containing either 0 or 1 mg triiodothyronine (T3) per kilogram. Birds were sampled at 28, 30, and 33 days. Measurements taken included in vitro lipogenesis (IVL), malic enzyme (ME) activity, isocitrate dehydrogenase, aspartate amino transferase, and the expression of the genes for ME, fatty acid synthase (FAS), and acetyl coenzyme carboxylase (ACC). Hypothyroidism decreased IVL and ME at 28 days of age; however, T3 supplementation for 2 days restored both IVL and ME. Paradoxically, continuing T3 replenishment for an additional 3 days decreased IVL but did not decrease ME activity. In contrast, supplemental T3 decreased IVL in euthyroid birds, regardless of the dosing interval, but had no effect on ME activity. Although methimazole decreased ME gene expression, there was only a transitory relationship between enzyme activity and gene expression when plasma T3 was restored with exogenous T3. These data may help to explain some of the apparent reported dichotomies in lipid metabolism elicited by changes in the thyroid state of animals. In addition, most metabolic changes in response to feeding T3 occurred within 2 to 5 days, suggesting that changes in intermediary metabolism preceded morphological changes. In conclusion, the thyroid state of the animal will determine responses to exogenous T3.     

Estrogen induces hyperlipidemia in fasted chicks

To determine whether the estrogen-induced hyperlipidemia is affected by fasting, male growing chicks were administered subcutaneously a single dose of 17 beta-estradiol (25 mg/kg body wt), and the hormone treatment lasted for 2 days with or without feed (Experiment 1). In the second experiment, chicks were initially fasted for 1 or 3 days, and then treated with the same dosage of 17 beta-estradiol as in Experiment 1 for 2 days without feed. Plasma and liver lipids, and the activities of hepatic malic enzyme, glucose-6-phosphate dehydrogenase, and hormone-sensitive lipase in the adipose tissue were determined. Compared with fed control chicks, estrogen treatment in fed birds resulted in a marked elevation of plasma lipids, especially triglyceride during the 2-day period (137 vs 2263 mg/dl). In fasted chicks, the present finding that estrogen also induced a marked hyperlipidemia is noteworthy. Upon estrogen treatment (Experiment 1), the level of plasma triglyceride in fasted birds increased about 16 times over that of the fasted control group (133 vs 2093 mg/dl). Even in chicks fasted for 5 days (Experiment 2), estrogen treatment resulted in a persistent hypertriglyceridemia (75 vs 1369 mg/dl). In fed chicks, estrogen treatment also induced a fatty liver with massive accumulation of triglyceride, but the liver of estrogen-treated/fasted chicks appeared to be normal. In both fed and fasted chicks, malic enzyme was found to be the major NADPH producing enzyme in the liver. Upon fasting, both malic enzyme and glucose-6-phosphate dehydrogenase activities decreased significantly (P less than 0.05). In fed chicks, the total activities of both enzymes increased with estrogen treatment, whereas the effect of hormone on these enzymes was less obvious in fasted chicks. The hormone-sensitive lipase activity in the adipose tissue was much lower in fed chicks compared with that of fasted birds (0.15 vs 0.33 nmol of oleic acid released/min/mg protein). Estrogen treatment in fed chicks had no effect on the hormone-sensitive lipase activity, but its activity was enhanced by the hormone treatment in fasted chicks. The present finding that hyperlipidemia persisted in estrogenized chicks during the fasting seems to indicate the complex nature of this hormonal influence on lipid metabolism.     

砷对兰州鲇组织中代谢酶活性及RNA和蛋白质含量影响

采用毒性试验方法,研究了安全浓度（1.288 mg/L）条件下亚砷酸钠（NaAsO2）对兰州鲇（Silurus lanzhouensis）脑、鳃、肝脏、肌肉4种组织中6-磷酸葡萄糖脱氢酶（G-6-PDH）和乳酸脱氢酶（LDH）活性,以及RNA和蛋白质含量的影响。结果表明,染毒21d时,As（Ⅲ）可显著降低4种组织中G-6-PDH和LDH活性、RNA和蛋白质含量（P0.05）。撤毒后21d,除脑和肝组织中蛋白质含量未恢复到对照组水平（P0.05）,肝脏中G-6-PDH活性超过了对照组水平（P0.05）外,其余各组织中G-6-PDH和LDH活性、RNA和蛋白质含量均可恢复到对照组水平（P0.05）。以上结果表明,As（Ⅲ）对兰州鲇组织中代谢酶活性具有明显的抑制作用,可致组织细胞RNA损伤和可溶性蛋白质减少,但这种影响是可逆的,撤毒后一定时间内可恢复到正常水平。       

Responses of chickens subjected to thyroid hormone depletion-repletion

The purpose of this experiment was to determine the relationship between lipid metabolism and the expression of specific genes in chickens fed methimazole to produce hypothyroidism. Male, broiler chickens growing from 14 to 28 days of age were fed diets containing 18% crude protein and either 0 or 1 g methimazole per kg of diet. At 28 days, these two groups were further subdivided into groups receiving 18% crude protein diets containing either 0 or 1 mg triiodothyronine (T(3)) per kg. Birds were sampled at intervals from 0 to 120 h. Measurements taken included in vitro lipogenesis (IVL), malic enzyme (ME), isocitrate dehydrogenase (ICD-NADP), aspartate aminotransferase (AAT) activities and the expression of the genes for ME, fatty acid synthase (FAS), NADP-ICD, AAT and acetyl coenzyme carboxylase (ACC). Gene expression was estimated with real time RT-PCR assays. Expression rates were noted as C(t)'s. Dietary methimazole decreased IVL and ME at 28 days of age. T(3) and supplementation for 1 day restored both IVL and ME. Paradoxically, continuing T(3) replenishment for a longer period decreased IVL without affecting ME activity. Although methimazole decreased ME gene expression, there was only a transitory relationship between enzyme activity and gene expression when plasma T(3) was replenished with exogenous T(3). These data explain the apparent dichotomies in lipid metabolism elicited by changes in the thyroid state of animals. Most metabolic changes in response to feeding T(3) occurred within a short period of time, suggesting that changes in intermediary metabolism preceded morphological changes. Furthermore, the thyroid state of the animal will determine responses to exogenous T(3).     

Effects of nicotine and vitamin E on glucose 6-phosphate dehydrogenase activity in some rat tissues in vivo and in vitro

Effects of nicotine, and nicotine + vitamin E on glucose 6-phosphate dehydrogenase (G-6PD) activity in rat muscle, heart, lungs, testicle, kidney, stomach, brain and liver were investigated in vivo and in vitro on partially purified homogenates. Supplementation period was 3 weeks (n = 8 rats per group): nicotine [0.5 mg/kg/day, intraperitoneal (ip)]; nicotine + vitamin E [75 mg/kg/day, intragastric (ig)]; and control group (receiving only vehicle). The results showed that nicotine (0.5 mg/kg, ip) inhibited G-6PD activity in the lungs, testicle, kidney, stomach and brain by 12.5% (p < 0.001), 48% (p < 0.001), 20.8% (p < 0.001), 13% (p < 0.001) and 23.35% (p < 0.001) respectively, and nicotine had no effects on the muscle, heart and liver G6PD activity. Also, nicotine + vitamin E inhibited G-6PD activity in the testicle, brain, and liver by 32.5% (p < 0.001), 21.5% (p < 0.001), and 16.5% (p < 0.001) respectively, and nicotine + vitamin E activated the muscle, and stomach G-6PD activity by 36% (p < 0.05), and 20% (p < 0.001) respectively. In addition, nicotine + vitamin E did not have any effects on the heart, lungs, and kidney G-6PD activity. In addition, in vitro studies were also carried out to elucidate the effects of nicotine and vitamin E on G-6PD activity, which correlated well with in vivo experimental results in lungs, testicles, kidney, stomach, brain and liver tissues. These results show that vitamin E administration generally restores the inactivation of G-6PD activity due to nicotine administration in various rat tissues in vivo, and also in vitro.     

Serum thyroid hormones and performance of offspring in ewes receiving propylthiouracil with or without melatonin

Two experiments were conducted during mid-gestation to examine effects in ewes of propylthiouracil (PTU) treatment alone or with melatonin on serum thyroid hormones, postpartum reproduction, and lamb performance. In the first experiment, beginning on day 0 (first day of treatment when all animals were 72.2+/-0.9 days of gestation), ewes received daily treatments (gavage) consisting of either 0mg (n=6) or 40 mg (n=6) PTU/kg body weight/day for 15 days. After 15 days, the 40 mg dosage was decreased to 20mg/kg body weight for an additional 20 days (35 days of PTU). Serum thyroxine (T4) did not differ (P>0.10) between groups through day 4; but on day 5, control females had a serum value of 67 ng/ml compared with 46 (+/-5)ng/ml for PTU-treated ewes (P=0.02). On the last day that 40 mg of PTU was administered, serum T4 averaged 67 and 7 (+/-5)ng/ml (P<0.001) in the two respective groups. Serum T4 remained low and was 80 and 1 ng/ml (P<0.001) in control and treated ewes on day 34. Serum T4 rose gradually after PTU but remained different from that observed in control ewes through day 48. Lambs from control and treated ewes had similar (P=0.46) T4 values at birth but lambs from PTU-treated ewes had lower (P=0.03) birth weights than did those from control ewes. Serum progesterone (P4) after parturition indicated a lack of cyclicity in all ewes. In the second experiment, beginning on day 0 (76.8+/-4.7 days of gestation), ewes received PTU as in Experiment 1. In addition, after 15 days of PTU, melatonin was given (i.m. injections at 5mg/day) for 30 days. Propylthiouracil decreased (P0.60) for lambs born to control and treated ewes. Female offspring of PTU+melatonin-treated dams reached puberty, became anestrus, and returned to cyclicity at similar (P>0.10) times to contemporary ewe lambs. Results indicate that 40/20mg PTU alone or with melatonin does not induce cyclicity after lambing in spring lambing ewes and has little effect on offspring performance.     

Piperine lowers the serum concentrations of thyroid hormones, glucose and hepatic 5'D activity in adult male mice.

Piperine, the main alkaloid of Piper nigrum fruits, was evaluated for its thyroid hormone and glucose regulatory efficacy in adult male Swiss albino mice. Its daily oral administration (2.50 mg/kg) for 15 days lowered the serum levels of both the thyroid hormones, thyroxin (T (4)) and triiodothyronine (T (3)) as well as glucose concentrations with a concomitant decrease in hepatic 5'D enzyme and glucose-6-phospatase (G-6-Pase) activity. However, no significant alterations were observed in animals treated with 0.25 mg/kg of piperine in any of the activities studied except an inhibition in serum T (3) concentration. The decrease in T (4), T (3) concentrations and in G-6-Pase were comparable to that of a standard antithyroid drug, Proylthiouracil (PTU). The hepatic lipid-peroxidation (LPO) and the activity of endogenous antioxidants, superoxide dismutase (SOD), and catalase (CAT) were not significantly altered in either of the doses. It appears that the action of P. nigrum on thyroid functions is mediated through its active alkaloid, piperine. We also suggest that a higher dose of piperine may inhibit thyroid function and serum glucose concentration in euthyroid individuals.     

Free fatty acids increase basal hepatic glucose production and induce hepatic insulin resistance at different sites

To investigate the sites of the free fatty acid (FFA) effects to increase basal hepatic glucose production and to impair hepatic insulin action, we performed 2-h and 7-h Intralipid + heparin (IH) and saline infusions in the basal fasting state and during hyperinsulinemic clamps in overnight-fasted rats. We measured endogenous glucose production (EGP), total glucose output (TGO, the flux through glucose-6-phosphatase), glucose cycling (GC, index of flux through glucokinase = TGO - EGP), hepatic glucose 6-phosphate (G-6-P) content, and hepatic glucose-6-phosphatase and glucokinase activities. Plasma FFA levels were elevated about threefold by IH. In the basal state, IH increased TGO, in vivo glucose-6-phosphatase activity (TGO/G-6-P), and EGP (P < 0.001). During the clamp compared with the basal experiments, 2-h insulin infusion increased GC and in vivo glucokinase activity (GC/TGO; P < 0.05) and suppressed EGP (P < 0.05) but failed to significantly affect TGO and in vivo glucose-6-phosphatase activity. IH decreased the ability of insulin to increase GC and in vivo glucokinase activity (P < 0.01), and at 7 h, it also decreased the ability of insulin to suppress EGP (P < 0.001). G-6-P content was comparable in all groups. In vivo glucose-6-phosphatase and glucokinase activities did not correspond to their in vitro activities as determined in liver tissue, suggesting that stable changes in enzyme activity were not responsible for the FFA effects. The data suggest that, in overnight-fasted rats, FFA increased basal EGP and induced hepatic insulin resistance at different sites. 1) FFA increased basal EGP through an increase in TGO and in vivo glucose-6-phosphatase activity, presumably due to a stimulatory allosteric effect of fatty acyl-CoA on glucose-6-phosphatase. 2) FFA induced hepatic insulin resistance (decreased the ability of insulin to suppress EGP) through an impairment of insulin's ability to increase GC and in vivo glucokinase activity, presumably due to an inhibitory allosteric effect of fatty acyl-CoA on glucokinase and/or an impairment in glucokinase translocation.     

Effect of hind limb muscle unloading on liver metabolism of rats

In response to decreased use, skeletal muscle undergoes an adaptive reductive remodeling. There is a shift in fiber types from slow twitch to fast twitch fiber types. Associated with muscle unloading is an increased reliance on carbohydrate metabolism for energy. The hind limb suspended (HLS) rat model was used as the experimental model to determine whether skeletal muscle unloading had any impact on the liver. We used a combination of actual enzyme assays and microarray mRNA expression to address this question. The GenMAPP program was used to identify altered metabolic pathways. We found that the major changes in the liver with HLS were increases in the expression of genes involved in the generation of energy fuels for export, specifically gluconeogenesis and lipogenesis. The expression of mRNA was increased (P<0.05) for three of the four enzymes involved in the regulation of gluconeogenesis pathway (pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase (G-6-Pase). Actual assay of enzymatic activity, in micromol . min(-1) . mg protein(-1) showed G-6-Pase (0.14+0.01 vs 0.17+0.01 P<0.05), fructose 1,6, bisphophosphatase (0.048+0.002 vs 0.054+0.002, P<0.07), and PEPCK (0.031+0.002 vs 0.038+0.012 (P<0.05) to be increased. We conclude that 1) atrophied muscle is not the only tissue to be affected by HLS, as there is also a response by the liver; and 2) the major changes in liver substrate metabolism induced by HLS appear to be limited to glucose and triglyceride production. The increase in glycolytic capacity in disused muscle is paralleled by an increase in glucogenic capacity by the liver.     

Effect of propylthiouracil on liver regeneration in rats after partial hepatectomy.

The effect of propylthiouracil (PTU) on the growth activity of intact liver and liver regenerating after partial (65-70%) hepatectomy (PH) was studied in rats. PTU (Propycil, Kali-Chemie, FRG) was dissolved in drinking water (1 g PTU per litre) and this was given to the rats, as their sole source of fluids, three days before PH and then up to the end of the experiment. In rats given PTU, marked inhibition of liver DNA synthesis and the mitotic activity of hepatocytes was found after PH. This effect was potentiated to some extent by partial inanition of the experimental animals given PTU, as demonstrated in a paired feeding test in control rats. PTU inhibition of DNA synthesis in intact and regenerating liver also took effect in thyroidectomized rats, even with substitution (thyroid hormone) therapy. The experiments demonstrated that the effect of propylthiouracil on DNA synthesis in the liver is mediated primarily by way of its direct effect on the liver.     

Effect of starvation and a protein diet on the amino acid metabolism enzyme activities of the organs of domestic fowl hatchlings

The activities of alanine and aspartate transaminases, adenylate deaminase, glutamine synthetase and glutamate and xanthine dehydrogenases have been measured in liver, yolk sac membrane, intestine and breast and leg muscle of domestic fowl hatchlings receiving for 3 or 5 days either a standard diet or hard boiled eggwhite as well as in 3 or 5 days starved animals. The patterns of activation of amino acid metabolism enzymes were fully comparable in protein-fed and starved groups with respect to fed controls; the differences with respect to the latter became more marked in 5- than in 3-days old chicks. In 5-days old chicks intestine alanine transaminase activity increased in parallel to that of liver in protein-fed animals but not in those starved, in agreement with an enhanced alanine transfer between both organs under this situation. Both, starvation and protein-feeding, induced a general decrease in the amino acid metabolizing ability of muscle. Glutamine (but not alanine) synthetizing capabilities were enhanced.     

Overexpression of acyl-CoA synthetase-1 increases lipid deposition in hepatic (HepG2) cells and rodent liver in vivo

Accumulation of intracellular lipid in obesity is associated with metabolic disease in many tissues including liver. Storage of fatty acid as triglyceride (TG) requires the activation of fatty acids to long-chain acyl-CoAs (LC-CoA) by the enzyme acyl-CoA synthetase (ACSL). There are five known isoforms of ACSL (ACSL1, -3, -4, -5, -6), which vary in their tissue specificity and affinity for fatty acid substrates. To investigate the role of ACSL1 in the regulation of lipid metabolism, we used adenoviral-mediated gene transfer to overexpress ACSL1 in the human hepatoma cell-line HepG2 and in liver of rodents. Infection of HepG2 cells with the adenoviral construct AdACSL1 increased ACSL activity >10-fold compared with controls after 24 h. HepG2 cells overexpressing ACSL1 had a 40% higher triglyceride (TG) content (93 +/- 3 vs. 67 +/- 2 nmol/mg protein in controls, P < 0.05) after 24-h exposure to 1 mM oleate. Furthermore, ACSL1 overexpression produced a 60% increase in cellular LCA-CoA content (160 +/- 6 vs. 100 +/- 6 nmol/g protein in controls, P < 0.05) and increased [(14)C]oleate incorporation into TG without significantly altering fatty acid oxidation. In mice, AdACSL1 administration increased ACSL1 mRNA and protein more than fivefold over controls at 4 days postinfection. ACSL1 overexpression caused a twofold increase in TG content in mouse liver (39 +/- 4 vs. 20 +/- 2 mumol/g wet wt in controls, P < 0.05), and overexpression in rat liver increased [1-(14)C]palmitate clearance into liver TG. These in vitro and in vivo results suggest a pivotal role for ACSL1 in regulating TG synthesis in liver.     

Experimental hypothyroidism inhibits delta-aminolevulinate dehydratase activity in neonatal rat blood and liver

The aim of this study was to investigate the potential relationship between hypothyroidism and delta-aminolevulinate dehydratase (delta-ALA-D) activity in rat blood and liver. Experimental hypothyroidism was induced in weanling rats by exposing their mothers to propylthiouracil (PTU) diluted in tap water (0.05% w/ v), ad libitum, during the lactational period (PTU group). Control (euthyroid) group included weanling rats whose mothers received just tap water, ad libitum, during the lactational period. Reverted-hypothyroid group (PTU + 3,3',5-triiodo-L-thyronine [T(3)]) included weanling rats whose mothers were exposed to PTU similarly to those in the hypothyroid group, but pups received daily subcutaneous injections of T(3) (20 microg/kg, from Postnatal Days 2-20). After the treatment, serum T(3) levels were drastically decreased (around 70%) in the PTU group, and this phenomenon was almost reverted by exogenous T(3). PTU decreased blood delta-ALA-D activity by 75%, and T(3) treatment prevented such phenomena. Erythrocytes and hemoglobin levels were increased by 10% in PTU-treated animals and higher increments (around 25%) were observed in these parameters when exogenous T(3) was coadministered. Dithiothreitol did not change blood delta-ALA-D activity of PTU-exposed animals when present in the reaction medium, suggesting no involvement of the enzyme's essential thiol groups in PTU-induced delta-ALA-D inhibition. PTU did not affect blood delta-ALA-D activity in vitro. These results are the first to show a correlation between hypothyroidism and decreased delta-ALA-D activity and point to this enzyme as a potential molecule involved with hypothyroidism-related hematological changes.     

Role of Amino Acid-catabolizing Enzymes in Urea Synthesis for Rats Treated with the Thyroid Hormone

The purpose of the present study was to determine whether the regulation of urea synthesis was mediated through the supply of nitrogen by amino acid-catabolizing enzymes and whether the concentration of acetylCoA would control the N-acetylglutamate concentration when the thyroid status was manipulated. Experiments were conducted on three groups of rats, each being given 6-propyl-2-thiouracil (PTU, thyroid inhibitor) without a triiodothyronine (T₃) treatment, or PTU + T₃, or neither PTU nor T₃ (control), respectively. The urinary excretion of urea, the liver concentration of N-acetylglutamate, and the hepatic activities of serine dehydratase, threonine dehydratase, alanine transaminase (GPT) and aspartate transaminase (GOT) in rats given PTU + T₃ were significantly lower than those in rats given PTU alone. The activity of glutamate dehydrogenase and the concentrations of free amino acids and acetylCoA in the liver of the PTU + T3-treated group were significantly higher than those in the group treated with PTU alone. These results suggest that the higher activity of amino acid-catabolizing enzymes in the hypothyroid (with PTU alone) rats is likely to stimulate urea synthesis.     

Biological activity of phenolic compounds. Hepatic cytochrome P-450, cytochrome b5, and NADPH cytochrome c reductase in chicks and rats fed phenolic monomers, polymers, and glycosides

Eight experiments were conducted to determine effects of a phenolic polymer (Kraft wood lignin, Indulin), phenolic glycosides (cane molasses and wood molasses), and phenolic monomers (vanillin, vanillic acid, ferulic acid, and p-coumaric acid) on liver cytochromes P-450, cytochrome b5, and NADPH cytochrome c reductase in chicks and rats. Chicks fed 6.0% lignin had a higher (P less than 0.01) cytochromes P-450 content than did chicks fed 0% fiber, 6.0% wood cellulose (Solka Floc), or 6.0% arenaceous flour. NADPH cytochrome c reductase activity was not affected by treatment. Chicks fed 12.0% wood molasses had a higher (P less than 0.06) cytochromes P-450 level than did chicks fed 0% fiber or 6.0% wood molasses. Cane molasses incorporated at both 6.0 and 12.0% of the diet induced (P less than 0.05) cytochromes P-450 content over those of control-fed birds. Chicks fed 6.0% lignin, with or without antibiotic (bacitracin:neomycin sulfate, 2:1), had a higher (P less than 0.01) cytochromes P-450 level than did chicks fed control diets, with or without antibiotic. Additionally, chicks fed 6.0% lignin had lower (P less than 0.01) intestinal diaminopimelic acid (DAP) levels than did chicks fed 0% fiber. Rats fed 0% fiber, 6.0% wood cellulose, 6.0% arenaceous flour, or 6.0% lignin exhibited no difference in cytochrome level or activity among treatments. Chicks fed 0.5% vanillin, 0.5% vanillic acid, 0.5% ferulic acid, or 0.5% p-coumaric acid had comparable cytochromes level and activity compared with chicks fed no phenolics. Chicks fed 0.5% p-coumaric acid had lower (P less than 0.05) rates of gain than did chicks fed control or other phenolic-containing diets. Rats fed these phenolics had similar cytochromes P-450 content among treatments.     

Modulation of rat liver mitochondrial antioxidant defence system by thyroid hormone

In the present study the effect of thyroid hormone (T(3)) on oxidative stress parameters of mitochondria of rat liver is reported. Hypothyroidism is induced in male adult rats by giving 0.05% propylthiouracil (PTU) in drinking water for 30 days and in order to know the effect of thyroid hormone, PTU-treated rats were injected with 20 microg T(3)/100 g body weight/day for 3 days. The results of the present study indicate that administration of T(3) to hypothyroid (PTU-treated) rats resulted in significant augmentation of oxidative stress parameters such as thiobarbituric acid reactive substances and protein carbonyl content of mitochondria in comparison to its control and euthyroid rats. The hydrogen peroxide content of the mitochondria of liver increased in hypothyroid rats and was brought to a normal level by T(3) treatment. Induction of hypothyroidism by PTU treatment to rats also resulted in the augmentation of total and CN-sensitive superoxide dismutase (SOD) activities of the mitochondria, which was reduced when hypothyroid rats were challenged with T(3). Although CN-resistant SOD activity of the mitochondria remained unaltered in response to hypothyroidism induced by PTU treatment, its activity decreased when hypothyroid rats were injected with T(3). The catalase activity of the mitochondria decreased significantly by PTU treatment and was restored to normal when PTU-treated rats were given T(3). Total, Se-independent and Se-dependent glutathione peroxidase activities of the mitochondria were increased following PTU treatment and reduced when T(3) was administered to PTU-treated rats. The reduced and oxidised glutathione contents of the mitochondria of liver increased significantly in hypothyroid rats and their level was restored to normal when hypothyroid rats were injected with T(3). The results of the present study suggest that the mitochondrial antioxidant defence system is considerably influenced by the thyroid states of the body.     

Activation of liver G-6-Pase in response to insulin-induced hypoglycemia or epinephrine infusion in the rat

This study was conducted to test the hypothesis of the activation of glucose-6-phosphatase (G-6-Pase) in situations where the liver is supposed to sustain high glucose supply, such as during the counterregulatory response to hypoglycemia. Hypoglycemia was induced by insulin infusion in anesthetized rats. Despite hyperinsulinemia, endogenous glucose production (EGP), assessed by [3-(3)H]glucose tracer dilution, was paradoxically not suppressed in hypoglycemic rats. G-6-Pase activity, assayed in a freeze-clamped liver lobe, was increased by 30% in hypoglycemia (P < 0.01 vs. saline-infused controls). Infusion of epinephrine (1 microg x kg(-1) x min(-1)) in normal rats induced a dramatic 80% increase in EGP and a 60% increase in G-6-Pase activity. In contrast, infusion of dexamethasone had no effect on these parameters. Similar insulin-induced hypoglycemia experiments performed in adrenalectomized rats did not induce any stimulation of G-6-Pase. Infusion of epinephrine in adrenalectomized rats restored a stimulation of G-6-Pase similar to that triggered by hypoglycemia in normal rats. These results strongly suggest that specific activatory mechanisms of G-6-Pase take place and contribute to EGP in situations where the latter is supposed to be sustained.     

Dietary cimetidine and copper in Eimeria acervulina-infected chicks

The effects of varying levels of cimetidine (N"-cyano-N-methyl-N'-(2-[(5-methylimidazol-4-yl)methylthio]-ethyl ) guanidine) on Eimeria acervulina (duodenal coccidiosis)-induced changes in gain, efficiency, duodenal pH, and liver copper concentration of chicks were investigated. In a preliminary trial, gain, efficiency, and duodenal pH were significantly reduced in chicks inoculated one time with 1 X 10(6) sporulated oocysts. Dietary addition of 121 ppm monensin (2-[5-ethyltetrahydro-5-[tetrahydro-3-methyl-5-[tetrahydro-6-hydro xy-6- (hydroxymethyl)-3,5-dimethyl-2H-pyran-2-yl]-2-furyl]-2-furyl]-9-hydroxy- beta-methoxy-alpha, gamma, 2,8-tetramethyl-1,6-dioxaspiro[4.5]decane-7-butyric acid) prevented these coccidiosis-induced aberrations. In subsequent trials, growth rate, feed efficiency, and duodenal pH were reduced by E. acervulina infection, but were unaffected (P greater than 0.10) by dietary addition of 0.01% cimetidine. Linear depressions (P less than 0.05) in gain and efficiency, however, were observed from 0.05 and 0.10% cimetidine additions. Dietary addition of 500 ppm copper increased liver copper levels thirtyfold (P less than 0.01) after 2 weeks. Significant coccidiosis X copper interactions were detected in gain, efficiency, duodenal pH reduction, and liver copper elevation of chicks repeatedly inoculated with 4 X 10(5) sporulated E. acervulina oocysts. Coccidiosis increased liver copper levels (P less than 0.01) of chicks fed excess copper an additional threefold compared with uninfected chicks fed excess copper. Dietary additions of 0.01, 0.05 or 0.10% cimetidine were ineffective in preventing coccidiosis-associated performance and duodenal pH depressions as well as the coccidiosis-induced liver copper elevation. Apparently, host response to cimetidine is minor in comparison to effects of coccidia on duodenal pH. Increased copper solubility at low duodenal pH may explain high tissue copper levels and enhanced copper toxicity due to coccidiosis.