Mitochondrial adenosine triphosphatase activity of hepatocytes in obstructive jaundice

The activity of adenosine triphosphatase (ATPase) in the mitochondria of hepatocytes in extrahepatic cholestasis was studied calorimetrically. Elevation of Na⁺−K⁺-ATPase, Ca²⁺-ATPase, and Mg²⁺-ATPase activities in the mitochondria of hepatocytes was found in rats after bile duct ligation. Peak activity levels of these three enzymes were found in the group that had been ligated for 7 days. The activities were found to be extremely high in rats in very poor physical condition and with very poor motor activity 7 days after ligation. In a clinical study, these activities were examined in 44 patients classified into three groups: group I, those with non-jaundice cholelithiasis; group II, those with obstructive jaundice caused by common bile duct stones, and group III, those with obstructive jaundice caused by extrahepatic malignancy. All patients were operated on and liver specimens were collected for study. Na⁺−K⁺-ATPase activity was 0.86±0.18, 1.87±0.40, and 1.92±0.32. (M±SE) μmole pi/mg protein per hour for groups I, II, and III, respectivety. Mg²⁺-ATPase activity was 0.86±0.18, 1.87±0.34, and 1.50±0.35 μmole pi/mg protein per hour for groups I, II, and III. Ca²⁺-ATPase activity was 1.01±0.26, 2.51±0.44, and 2.08±0.51 μmole pi/mg protein per hour for groups I, II, and III. The values in groups II and III were significantly higher than those in group I. Elevation of these ATPase activities was clear in obstructive jaundice. These results may be due to the disturbed metabolism of hepatocytes or even to the cessation of metabolism, and hepatocytes try to reach a compensatory status during cholestasis.     

Glutathione and glutathione-related enzyme activities of male and female rat hepatocytes under various culture conditions

 The effect of culture medium on glutathione (GSH) dependent detoxification defence system of primary cultured hepatocyte from either male or female rats was studied. Intracellular reduced (GSH) and oxidized glutathione (GSSG), and six GSH-related enzyme activities, including GSH peroxidase (GSH Px), GSH reductase (GSH Rd), cytosolic GSH S-transferase (cGST), microsomal GSH S-transferase (mGST), γ-glutamyl transpeptidase (GTP), and γ-glutamylcysteine synthetase (GCS), were investigated during a 6-day culture. Media free of fetal bovine serum (FBS) and with 2.5 or 10% FBS were used. Whatever the medium, there was an initial increase of intracellular GSH and GSSG, a threefold increase of GSH at day 3 and fourfold increase of GSSG at day 4, later decreasing to their original level at day 6. The activities of all six GSH-related enzymes of male and female hepatocytes remained relatively stable during the first 72 h, then gradually decreased to 50–80% of initial activities. With the exception of cGST, time-course profiles of other enzyme activities were not significantly different among various media. In both sexes, higher cGST activity was maintained for cells cultured in the presence of FBS. Results of immunoblotting analysis of cytosolic GST isozymes indicate that the placental form of GST (Yp) was markedly increased after plating and the extent of increase of Yp was higher in the presence of FBS. Despite the culture medium, the level of GST isoform Ya was maintained steadily for 6 days, however, Yb was maintained during the first 3 days and then decreased. In terms of the gender difference, GSH Px and GTP activities of hepatocytes from females were significantly greater than of males over the entire culture period. Results indicate that FBS seems not to be absolutely essential in maintaining GSH level and most of the GSH-related enzyme activities in rat hepatocytes. Furthermore, GSH levels and GSH-related enzyme activities of hepatocytes from female rats were similar to those from male rats. Received: 10 January 1996/Accepted: 3 May 1996     

Iron acquisition and hemolysin production by Campylobacter jejuni.

Campylobacter jejuni strains were tested for their ability to acquire iron from various iron sources present in humans. Hemin, hemoglobin, hemin-hemopexin, and hemoglobin-haptoglobin stimulated the growth of C. jejuni strains in low-iron medium. Transferrin, lactoferrin, and ferritin were unable to provide iron to the strains tested. Derivatives of the naturally transformable C. jejuni strain 81-176 were isolated on the basis of their inability to use hemin as an iron source. These mutants were also unable to use hemoglobin, hemin-hemopexin, or hemoglobin-haptoglobin as iron sources. Some mutants lacked a 71,000-Da iron-regulated outer membrane protein, while others appeared to retain all of their outer membrane proteins. Growth curves and a recombination experiment that exploited natural transformation were used to further characterize the mutants. A hemolytic activity was shown to be produced by several C. jejuni strains, but it did not appear to be iron regulated.