Glutathione fasting

In comparative kinetic studies we have investigated the reaction between chromate and cysteamine, mercaptoethanol and thiolactic acid, at pH 7.4 (1 M Tris HCl) and 25 °C. All the reactions appear to be first order with respect to both chromate and thiol. The second order rate constants are listed in Table 2. The rates of chromate reduction for the various monothiols follows the order cysteine > cysteamine > glutathione (fast phase) > penicillamine > mercaptoethanol > glutathione (slow phase) > thiolactic acid. 

Furthermore, depletion of hepatic GSH induced chemically or by fasting augmented hepatic I/R-induced enzyme release and promoted lipid peroxidation (Jennische, 1984 Stein et al., 1991) Benoit et al. (1992) have used portacaval-shunted rats as a model of chronic hepatic ischaemia, and were able to show decreases in total levels of SOD and xanthine dehydrogenase, but no significant change in catalase or glutathione peroxidase. 

Table 4 Rate constants for the fast ( fast) and slow [ 2(slow) for the second-order path and i(slow) for the first-order path] reactions for the addition of glutathione (GSH) to 47, 48, 52, and 53 in PBS at pH 7.4 and for the addition of thiophenol (PhSH) to 54-56 in methanol... 

Rates of reaction were moderately fast. Glutathione reacted rapidly in DMS0-rf6/D20 ( 2 ° ca 2 X 10 lmol s ) and a series of A-benzoyloxy-A-benzyloxybenzamides (139) and (L)-cysteine ethyl ester in methanol-(f4 reacted with low a values (8-16 kcal mol ) and negative AS (—19 to —43 calK mol ), similar to their reaction with anilines. Bimolecular rate constants at 298 K (Table 8) correlated positively with Hammett a constants with slightly lower sensitivity p =. as opposed to p =. l for A-methylaniline). ... 

Deterding, L. J., Srinivas, P., Mahmood, N. A., Burka, L. T., and Tomer, K. B. (1989). Fast atom bombardment and tandem mass spectrometry for structure determination of cysteine, N- acety I cyste i n e, and glutathione adducts of xenobiotics. Anal. Biochem. 183 94-107. 

Haroldsen, P. E., Reilly, M. H., Hughes, H., Gaskell, S. J., and Porter, C. J. (1988). Characterization of glutathione conjugates by fast atom bombardment/tandem mass spectrometry. Biomed. Environ. Mass. Spectrom. 15 615-621. 

Siegers, C.P., Bartels, L., and Riemann, D., Effects of fasting and glutathione depletors on the GSH-dependent enzyme system in the gastrointestinal mucosa of the rat, Pharmacology, 38,121, 1989. 

Based on the coincidence of CZE- and CIEF-ICP-MS results with the formerly two-dimensionally gained results these fast techniques were used to elucidate the trend of Se species in human milk at different lactation stages [33], These trends are shown in Figure 17.7. It is obvious that the observed behavior (protein-associated Se decreases as lactation proceeds) is similar to glutathione-bound Se, whilst SeC increases. This may be of specific importance due to the central role of SeC in the human metabolism of Se. 

A separate pool has been proposed for the nucleus however, that finding remains in dispute. Mitochondrial glutathione is a separate physiological pool of glutathione in agreement with the observation that the liver has two pools of GSH. One has a fast (2-hr) and the other a slow (30-hr) turnover. In freshly isolated rat hepatocytes, the mitochondrial pool of GSH (about 10% of the total cellular pool) has a half-life of 30 hr while the half-life of the cytoplasmic pool is 2 hr. It has been concluded that the mitochondrial pool represents the stable pool of GSH observed in whole animals. 

Male rats used for the perfusion experiments were maintained under established conditions and were fasted 16-24 hours prior to surgery as previously described (35). In the first series of studies the luminal perfusate was at pH 4.2. This perfusate consisted of M199 tissue culture medium which contained a variety of amino acids, vitamins and minerals plus glucose. The perfusate was supplemented (at 110 umolar) with L-histidine HCl, L-cysteine, L-methionine, L-tryptophan, 2-picolinic acid, citric acid, or reduced glutathione. The mixture was Infused into the lumen at 0.39 ml per min for 20 min and 0.10 ml per min for the final 40 min of the experiments. The small Intestine was then removed and mucosal... 

Hepatotoxicity from paracetamol overdose can occur with single doses as low as 10-15 g. The risk factors for hepatotoxicity in excessive doses include induction of cytochrome P450 enzymes malnutrition or fasting, due to reduced glutathione stores and reduced glucuronidation chronic alcohol use and age over five years [8, 13]. 

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