Dichloroacetate-induced changes in liver of normal and diabetic rats.

Dichloroacetate (DCA) was administered orally to normal (nondiabetic) and streptozotocin-diabetic rats in a dose of 1000 mg/day/kg rat wt. One group of diabetic animals received DCA both orally and intraperitoneally. DCA therapy lowered the blood glucose values of diabetic animals but did not alter values in nondiabetic rats. The hepatic activity of glucokinase and pyruvate kinase were significantly lower in both DCA-treated nondiabetic and DCA-treated diabetic animals than values observed for untreated animals. However, DCA therapy was accompanied by remarkable increases in the activities of glucose-6-phosphate dehydrogenase and malic enzyme in both nondiabetic and diabetic animals. Glucose-6-phosphate dehydrogenase was 3-fold higher in DCA-treated nondiabetic animals whereas malic enzyme activity was 10-fold higher in the treated animals than observed in the untreated animals. Similar changes, although smaller in magnitude, were observed for these enzymes in the DCA-treated diabetic animals. Although DCA therapy was accompanied by a significant increase in the wet weights of the liver for both nondiabetic and diabetic animals, no morphological changes were seen by light or electron microscopy. Our observations coupled with those of previous investigators suggest that DCA therapy may have an important role in pyruvate metabolism and may lower the blood glucose concentration by inhibiting hepatic gluconeogenesis.     

Ion transport in liver mitochondria from normal and thyroxine-treated rats

Liver mitochondria isolated from rats 24 h after a single subcutaneous injection of 8 mg thyroxine per kilogram body weight were compared with those isolated from control rats that received injections of isotonic saline at the same time. The mitochondria isolated from the thyroxine-treated rats show higher rates of energy-dependent K⁺ and phosphate accumulation than those from control animals. It was also found that mitochondria from the hormone-treated animals required a larger addition of Ca²⁺/mg mitochondrial protein in order to uncouple oxidative phosphorylation, and showed smaller tendency to swellin vitro under energizing conditions. The data obtained on ion movements support previous observations that the stimulation of the basal rate of mitochondrial respiration by thyroxine is associated with an increase in the transmembrane protonic electrochemical potential difference, and indicate thatin vivo the hormone raises the intramitochondrial concentration of K⁺ and phosphate.     

Nicotinamide coenzyme content in the normal and regenerating liver of rats

The content of NADH and NADPH was measured in the intact and regenerating rat liver. In the intact rat liver, the content of NAD+, NADH, NADP+ and NADPH was 235 +/- 6.4, 66.6 +/- 4.3, 73.3 +/- 2.5 and 148.0 +/- 4.6 micrograms/g crude liver weight, respectively. Seasonal alterations in the rat liver content of coenzymes were established. No changes were found in the content of nicotinamide coenzymes in the regenerating liver 4 and 18 h after operation. Twenty-four hours after operation, a 25.6% increase in the content of NAD+ and a 57.8% reduction in the NADH content were recorded in the liver of hepatectomized animals. At the same time the total content of NAD+ plus NADH changed but insignificantly (14.7%). The total content of NADP+ plus NADPH dropped by 29.8% (within the above period). Thirty-two hours after operation the content of all the nicotinamide coenzymes returned to the initial level.     

Dynamics of glycogen content in the normal and cirrhotic liver following glucose administration to starving rats

Using biochemical, cytofluorimetric and television cytophotometric methods, glycogen contents were studied in normal and cirrhotic rat liver at various intervals after glucose administration to fasting animals. The obtained data indicate that after a 48 h fasting glycogen contents in normal and cirrhotic liver are equally poor. A marked rise of glycogen content in cirrhotic liver was observed only 20-30 min after glucose administration to rats. It has been established that at all intervals after glucose administration to rats hepatocytes of the portal lobule zone, both in normal and in cirrhotic liver, accumulate more glycogen than those of the central zone. Again, the intensity of glycogen accumulation in cirrhotically altered liver is significantly lower than in normal liver, due, presumably, to a lower rate of glycogen synthesis in pathologically changed liver.     

Proteins from different classes of liver nuclei in normal and thioacetamide-treated rats

1. In normal rats the amounts of each of the main types of nuclear protein, i.e. soluble proteins, histones, non-histone chromosomal proteins and residual proteins, vary within the different classes of rat liver nuclei fractionated by zonal centrifugation. 2. Heterogeneity is observed in the non-histone chromosomal proteins prepared from different classes of liver nuclei. These differences were observed by analysis of the proteins both by sodium dodecyl sulphate-polyacrylamide-gel electrophoresis and electrofocusing electrophoresis. They are most evident between the non-histone chromosomal proteins obtained from stromal and parenchymal nuclei. However, some differences are also found for the parenchymal nuclei, between the diploid parenchymal and the tetraploid parenchymal, and between them and the nuclei involved in the synthesis of DNA respectively. 3. Drastic alterations in the nuclear proteins are found after the administration of thioacetamide. The changes observed are complex and not uniform. They vary with the age of the animal and the type of nucleus. In general an increase in the soluble proteins and non-histone chromosomal proteins and a decrease in the residual proteins is observed. There is a decrease in the specific radioactivity of soluble and residual proteins. 4. Electrophoretic analysis of the non-histone chromosomal proteins showed that specific changes occurred after administration of thioacetamide, which are different in adolescent and young adult rats.