Hepatic export of glutathione and uptake of constituent amino acids, glutamate and cysteine, in broilers in vivo

A fabricated electro-spun sensor based on Lake Red C pigments doped into PAN (polyacrylonitrile) nano-fibers for electrochemical detection of Aflatoxin B1 in poultry feed and serum samples

The aim of this work was to fabricate a novel nano-fiber modified electrode, involving Lake Red C (LRC) pigments doped into electrospun polyacrylonitrile (PAN) fibrous films.

Antioxidant enzyme activities and mitochondrial fatty acids in pulmonary hypertension syndrome (PHS) in broilers

Major objectives of this study were to assess antioxidant protection and fatty acid profile in lung mitochondria and whole liver in broilers with pulmonary hypertension syndrome [(PHS; with and without high dietary vitamin E (VE)] (Experiment 1) and in broilers that did not develop PHS but were genetically selected (S) or not selected (NS) for resistance to PHS (Experiment 2). In Experiment 1, lung mitochondrial glutathione peroxidase (GSH-Px) activity was elevated in broilers with PHS compared to controls, broilers fed high VE, and broilers fed high VE with PHS (VE-PHS), but there were no differences in GSH reductase (GSH-Rd) among groups. In liver tissue, GSH-Px was also elevated by PHS but was lower in VE and VE-PHS groups than in controls. There were no differences in liver GSH-Rd, superoxide dismutase (SOD), or gamma-glutamylcysteine synthetase (gamma-GCS) activities with the exception that gamma-GCS was higher in the VE-PHS group than in the other groups. In Experiment 2, S lung mitochondria exhibited lower GSH-Px and higher GSH-Rd compared to NS broilers. In the liver, there were no differences in GSH-Px, GSH-Rd, or gamma-GCS, but SOD was lower in S compared to the NS broilers. High VE increased the percentage of saturated fatty acids and decreased the percentage of unsaturated fatty acids in lung mitochondria in Experiment 1; there were no differences in fatty acid content between S and NS mitochondria in Experiment 2. Thus, it appears that GSH recycling enzyme activities are affected by PHS and high VE presumably in response to differences in oxidative stress and that genetic resistance to PHS is associated with an inherently better capability to metabolize oxidants in lung mitochondria. The increase in saturation of lung mitochondrial fatty acids with high dietary VE would presumably make them more resistant to oxidative stress and, thus, reduce the level of PHS-induced oxidative stress.

Uptake of DL-2-hydroxy-4-methylthio-butanoic acid (DL-HMB) in the broiler liver in vivo

The methionine source DL-2-hydroxy-4methylthio-butanoic acid (DL-HMB; Alimet feed supplement) is widely used in the poultry industry. The purpose of this study was to determine the capacity of the broiler liver to remove DL-HMB from the circulation. Cannulae were implanted in the carotid artery and hepatic and hepatic portal veins in anesthetized male broilers (3.33 +/- 0.13 kg BW). In Experiment 1, birds (n = 5) were infused with DL-HMB solutions (diluted in saline, pH 7.2 to 7.4) into the hepatic portal vein at rates ranging from 4.4 to 22 mg/min per kg BW, whereas in Experiment 2, birds (n = 6) were infused with DL-HMB at rates ranging from 2.2 to 4.4 mg/min per kg BW. Plasma samples from each vessel were obtained before and after each 10-min DL-HMB infusion period with a 10-min clearance period allowed between each DL-HMB infusion. Regression analysis revealed a highly significant correlation in the amount of DL-HMB entering the liver via afferent vessels (afferent DL-HMB) and DL-HMB removed by the liver (y = 0.86(x) - 173, r2 = 0.98). The slope of this regression indicates that 86% of DL-HMB entering in afferent blood (i.e. from both the hepatic artery and hepatic portal vein) was removed or that the liver apparently metabolized 86% of the DL-HMB that entered the liver. The results indicate that the broiler liver has the capacity to remove DL-HMB from the circulation far in excess of that needed to metabolize DL-HMB that would enter the liver following gastrointestinal absorption in birds fed a conventional poultry diet. In addition, present results implicate the liver as a major site of removal from circulation and further metabolism of DL-HMB in chickens.

The hepatic extraction of plasma free amino acids and response to hepatic portal venous infusion of methionine sources in anesthetized SCWL males (Gallus domesticus)

This study was conducted to investigate the hepatic extraction of plasma free amino acids in anesthetized Single Comb White Leghorn (SCWL) males (Gallus domesticus). SCWL males were anesthetized and implanted with cannulae in the carotid artery, hepatic vein, hepatic portal vein and the left hepatic duct. Free amino acids in plasma and bile were determined before, during and after 30-min infusions of Saline (control), DL-Methionine (DL-Met) or DL-2-hydroxy-4-methylthio-butanoic acid (DL-HMB) into the hepatic portal vein. Hepatic extraction rates (HER) of amino acids were calculated based on the concentration of amino acids in plasma multiplied by estimations of blood flow in the hepatic portal vein, hepatic artery and hepatic vein. For the non-essential amino acids, alanine had the highest HER (46%). The liver also removed more than 20% of hepatic inflow of tyrosine and asparagine with substantial extraction (14-18%) of serine, glycine and glutamine, also. In contrast, less than 5% of hepatic inflow of glutamate and cystine were removed by liver. For the essential amino acids, HER for methionine, histidine and phenylalanine were 30, 14 and 17%, respectively, with less than 5% for branched-chain amino acids, lysine, arginine and threonine. Biliary secretion of amino acids represented a small percentage (<0.2%) of total hepatic extraction turnover of the amino acids. Infusion of methionine sources, DL-Met and DL-HMB, had no effect on hepatic metabolism of amino acids other than methionine. The results demonstrated for the first time, the hepatic extraction of circulating free amino acids in avian species in vivo.

Efficacy of N-acetylcysteine to reduce the effects of aflatoxin B1 intoxication in broiler chickens

N-acetylcysteine (NAC) has been used safely in humans and in other mammals as an antidote against several toxic and carcinogenic agents, including aflatoxin B1 (AFB1). The aim of this study was to evaluate the capability of dietary supplementation with NAC to ameliorate the effects of subacute intoxication with AFB1 in broiler chickens. One hundred twenty male Hubbard 1-d-old chickens were allocated into one of four dietary treatments: 1) control group without treatment, 2) purified AFB1 added to diet (3 mg/kg of feed) for 21 d, 3) NAC (800 mg/kg BW, daily), or 4) AFB1 plus NAC at the same doses as Groups 2 and 3. Broilers treated with AFB1 plus NAC were shown to be partially protected against deleterious effects on BW (57.8%), daily weight gain (49.1%), feed conversion index (21.4%), plasma and hepatic total protein concentration (45.2, 66.7%), plasma alanine aminotransferase (67.4%), hepatic glutathione-S-transferase (18.8%), and reduced glutathione liver concentration (75.0%). In addition, they showed less intense liver fading, friable texture, and microvesicular steatosis. In the kidney, thickening of glomerular basement membrane was also less severe in NAC+AFB1-treated chickens than in AFB1-treated chickens. Our results suggest that NAC provided protection against negative effects on performance, liver and renal damage, and biochemical alterations induced by AFB1 in broiler chickens. Effects of NAC alone on chick performance were also evaluated. Addition of NAC to diet (800 mg/kg BW) did not negatively affect feed consumption, conversion index, or serum chemistry and did not induce structural changes in the liver or kidney.

Biliary glutathione secretion in male single comb white leghorn chickens after inhibition of gamma-glutamyl transpeptidase

The amount of hepatic export of glutathione into bile and the importance of gamma-glutamyl transpeptidase (gammaGT) activity for catabolizing glutathione in the bile duct, have not been reported previously for domestic fowl. Therefore, the primary objective of this study was to establish baseline values of biliary glutathione, and a secondary objective was to investigate the effect of acivicin (AT-125; a gammaGT inhibitor) on biliary glutathione in the chicken. Cannulae were placed in the carotid artery (to measure blood pressure) and into the left bile duct of anesthetized male Single Comb White Leghorn (SCWL) chickens (n = 5; 17 to 18 wk). The right bile duct was clamped between the liver and gall bladder. Bile samples were collected at 15-min intervals into microcentrifuge tubes (on ice) containing serine borate and iodoacetic acid to prevent glutathione oxidation. After two samples were obtained to establish baseline values, retrograde infusion of AT-125 (30 microLmol/kg BW) was given to inhibit gammaGT activity in the biliary tree. Systemic blood pressure of the birds remained above 100 mm Hg throughout each experiment (90 to 120 min). Bile flow did not change significantly during the experiment and ranged between 0.15+/-0.03 and 0.20+/-0.07 mL/15 min per kg BW. Baseline biliary secretion values of reduced glutathione (GSH), oxidized glutathione (GSSG), and total glutathione (TGSH) were 4.6, 5.9, and 17 nmol/min per kg BW. After AT-125 infusion, biliary GSH levels increased from 15 to 31 nmol/min per kg BW, indicating that considerable gammaGT-mediated catabolism of GSH occurred in the biliary tree of SCWL males. These results indicate that considerable turnover of GSH in the livers of domestic chickens is due to biliary excretion and that substantial recovery of GSH occurs through activity of gammaGT in the biliary tree.

Hepatic and extra-hepatic stimulation of glutathione release into plasma by norepinephrine in vivo

Studies were conducted to determine the effect of norepinephrine (NE) on reduced glutathione (GSH) and oxidized glutathione (GSSG) export from hepatic and extra-hepatic tissues in vivo. Anesthetized Single Comb White Leghorn (SCWL) males were implanted with cannulae in the carotid artery, hepatic vein (HV) and hepatic portal veins (PV), and the left bile duct. In Experiment 1, GSH and GSSG in hepatic and portal venous plasma and bile were determined prior to, during, and following two 20-min infusions of NE (2 and 10 microg/min per kg BW) into the hepatic PV. The lower NE infusion rate increased hepatic venous GSH (indicative of increased GSH export into liver sinusoids) without affecting systemic or hepatic vascular pressures; however, it had no affect on portal venous GSH. The higher NE infusion rate increased GSH in the HV and hepatic PV (indicative of extra hepatic export of glutathione) as well as systemic pressure, hepatic and portal venous pressures, and the transhepatic pressure gradient. Biliary secretion of GSH and GSSG was unaffected by either rate of NE infusion in Experiment 1. In Experiment 2, pretreatment of birds with phentolamine, an alpha-adrenergic receptor blocker (alpha-block), abolished sinusoidal export GSH as well as the ability of NE to stimulate GSH release from hepatic and extra-hepatic tissue. Although HV and PV pressures were lower in alpha-block birds compared with controls, there were no differences in the transhepatic pressure gradient between groups. Plasma GSSG was below the limits of detection in Experiments 1 and 2. The combined results of Experiments 1 and 2 indicate that hepatic export of GSH was independent of changes in systemic or hepatic vascular pressures or changes in the transhepatic pressure gradient. The results of these studies are the first to demonstrate that export of GSH into plasma in vivo is mediated by an alpha-receptor-mediated mechanism in hepatic and extra-hepatic tissues. The findings may be particularly important with regard to antioxidant homeostasis of animals during periods of stress.

Measurements of pulmonary arterial pressure in anesthetized male broilers at two to seven weeks of age

Pulmonary hypertension (an elevated pulmonary arterial pressure) is the defining symptom of the pathophysiological progression leading to pulmonary hypertension syndrome (ascites) in broilers. Previously, closed-thorax techniques had not been reported for measuring the pulmonary arterial pressure in young (<5 wk of age) broilers. The objective of this research was to evaluate continuous pulmonary arterial pressure in anesthetized male broilers at weekly intervals (2 to 7 wk of age) by inserting a cannula directly into the pulmonary artery. Body weights, heart rates, and the right:total ventricular weight ratio were also recorded. Clinically healthy individuals were selected from two separate hatches without prior assessment of electrocardiograms or the percentage of saturation of hemoglobin with oxygen. The pulmonary arterial pressure increased (P < or = 0.05) from 20 to 25 mm Hg between Weeks 2 and 3, remained at approximately 25 mm Hg during Weeks 4 and 5, and then returned to 19 mm Hg during Weeks 6 to 7. Body weight increased with age, the heart rate and body weight-normalized right and total ventricular weights remained constant through Week 5, and the right:total ventricular weight ratio remained constant through Week 7. This technique is useful for determining age-related changes in pulmonary arterial pressure that may contribute to a mismatch between pulmonary vascular capacity and cardiac output in apparently healthy broilers during the pathogenesis of pulmonary hypertension syndrome.

Depletion of cellular glutathione by conditions used for the passaging of adherent cultured cells

Cultured cells are commonly exposed to trypsin-containing solutions in order to prepare cell suspensions suitable for subculture. Conditions used to release and disperse monolayers of cultured murine hepatoma 1c1c7 and human breast epithelial MCF10A cells caused the loss (40-95%) of cellular glutathione (GSH), but did not affect viability. Glutathione contents returned to pretrypsinization values within 24 h of replating. In contrast, the GSH contents of cultured rat hepatoma 5L cells were not affected by trypsinization. Exposure of 1c1c7 cultures to H(2)O(2) or etoposide 1 or 24 h after replating resulted in concentration-dependent cytostatic and cytotoxic effects. The concentration-response curves defining the cytostatic and cytotoxic effects of etoposide, and the cytostatic effects of H(2)O(2) were not influenced by the timing of toxicant addition. However, 1c1c7 cultures treated with H(2)O(2) 1 h after replating were more susceptible to the cytotoxic actions of the peroxide than cultures treated 24 h after plating. These studies show that conditions commonly used for the passaging of cultured cells can lead to a transient, but profound loss of GSH in some cell lines. Furthermore, the outcome of cytotoxicity analyses can be influenced by the time elapsed between the plating of cultures and the addition of toxicant.