[Rat brain and liver glutamine synthetase and gamma-glutamyltransferase activity in alloxan diabetes (IV)]. / Glutaminsintetaznaia i gamma-glutamiltransferaznaia aktivnost' mozga i pecheni krys pri alloksanovom diabete (soobshchenie IV).

Glutamine synthetase and gamma-glutamyltransferase activities of brain and liver homogenates of rats suffering from alloxan diabetes were determined in the soluble fraction (fraction 1) and in that obtained after treatment with 0.2 percent deoxycholate (fraction 2). The results obtained indicate that the activities of these enzymes in homogenates of brain and liver of diabetic animals does not differ from that of normal animals. gamma-Glutamyltransferase activity of brain is significantly reduced (about 5 fold) in the soluble fraction while glutamine synthetase activity is not much changed. The activities of glutamine-synthetase and gamma-glutamyltransferase of the 2-nd fraction obtained from rat brain and liver are very much higher than in the first fraction and are not considerably different from the activities observed in normal animals. In contrast to brain, glutamine synthetase and gamma-glutamyltransferase activities of liver of diabetic animals do not differ from the activities observed in normal animals, both in the homogenates and in the 1-st and 2-nd fractions.

[Glutamine synthetase and glutaminase activity in the brain and liver homogenates and subcellular fractions of rats with alloxan diabetes (3)]. / Glutaminsintetaznais i glutaminaznaia aktivnost' v gomogenatakh i subkletochnykh fraktsiiakh mozga i pecheni u krys pri alloksanovom diabete.

Glutaminsynthetase activity has been determined in microsomal and soluble fractions of brain and liver of normal and alloxan diabetic rats and glutaminase activity in homogenates and mitochondrial fractions. The results obtained indicate that in brain of diabetic animals glutaminesynthetase activity of microsomal fractions is changed very slightly while that of the soluble fraction is marked reduced. In liver tissue enzyme activity is significantly decreased in both microsomal and soluble fractions. In homogenates of brain tissue of diabetic animals glutaminase does not differ markedly from that of control animals both in the presence and absence of activators (phosphate, aspartate, bicarbonate). In homogenates of liver, in the absence of activators, glutaminase activity is greater in diabetic animals than in controls, it is not much changed in the presence of phosphate and decreases in the presence of bicarbonate and aspartate. In diabetic animals, in the presence of phosphate, glutaminase activity of brain mitochondrial fractions increases while that of liver mitochondrial fractions does not change. It is interesting to note that in the absence of activators glutaminase activity is absent in both brain and liver mitochondria while it is quite high in homogenates.