Mg2+-ATPase activity in suckling rat brain regions in galactosaemia in vitro. l-Cysteine and glutathione effects

Effect of leptin administration on membrane-bound adenosine triphosphatase activity in ethanol-induced experimental liver toxicity

Hepatic injury elicits intracellular stress that leads to peroxidation of membrane lipids accompanied by alteration of structural and functional characteristics of the membrane, which affects the activity of membrane-bound ATPases. We have explored the effect of leptin on hepatic marker enzyme and membrane-bound adenosine triphosphatases in ethanol-induced liver toxicity in mice. The experimental groups were control, leptin (230 μg kg−1, i.p. every alternate day for last 15 days), alcohol (6.32 g kg−1, by intragastric intubation for 45 days), and alcohol plus leptin. Ethanol feeding to mice significantly (P < 0.05) elevated the plasma leptin, alanine transaminase (ALT), alkaline phosphatase (ALP), γ-glutamyl transpeptidase (GGT) and hepatic lipid hydroperoxides (LOOH), and plasma and hepatic total ATPases, Na+, K+-ATPase and Mg2+-ATPase. There was a significant decrease in Ca2+-ATPase and reduced glutathione (GSH). Leptin injections to ethanol-fed animals further elevated the levels of hepatic LOOH, plasma and hepatic total ATPases, Na+, K+-ATPase and Mg2+-ATPase, while the Ca2+-ATPase and GSH were decreased significantly. In addition, leptin administration was found to increase the plasma levels of leptin, ALT, ALP, GGT, Na+ and inorganic phosphorous, and decrease the levels of K+ and Ca2+ in ethanol-fed mice. These findings were consistent with our histological observations, confirming that leptin enhanced liver ailments in ethanol-supplemented mice.

The roles of galactitol, galactose-1-phosphate, and phosphoglucomutase in galactose-induced toxicity in Saccharomyces cerevisiae

The uptake and catabolism of galactose by the yeast Saccharomyces cerevisiae is much lower than for glucose and fructose, and in applications of this yeast for utilization of complex substrates that contain galactose, for example, lignocellulose and raffinose, this causes prolonged fermentations. Galactose is metabolized via the Leloir pathway, and besides the industrial interest in improving the flux through this pathway it is also of medical relevance to study the Leloir pathway. Thus, genetic disorders in the genes encoding galactose-1-phosphate uridylyltransferase or galactokinase result in galactose toxicity both in patients with galactosemia and in yeast. In order to elucidate galactose related toxicity, which may explain the low uptake and catabolic rates of S. cerevisiae, we have studied the physiological characteristics and intracellular metabolite profiles of recombinant S. cerevisiae strains with improved or impaired growth on galactose. Aerobic batch cultivations on galactose of strains with different combinations of overexpression of the genes GAL1, GAL2, GAL7, and GAL10, which encode proteins that together convert extracellular galactose into glucose-1-phosphate, revealed a decrease in the maximum specific growth rate when compared to the reference strain. The hypothesized toxic intermediate galactose-1-phosphate cannot be the sole cause of galactose related toxicity, but indications were found that galactose-1-phosphate might cause a negative effect through inhibition of phosphoglucomutase. Furthermore, we show that galactitol is formed in S. cerevisiae, and that the combination of elevated intracellular galactitol concentration, and the ratio between galactose-1-phosphate concentration and phosphoglucomutase activity seems to be important for galactose related toxicity causing decreased growth rates.