Transient activation of hepatic glycogenolysis by thrombin in perfused rat livers

Development of a small-scale bioreactor for drug metabolism studies maintaining hepatospecific functions

1. The aim of the study was the development of a small-scale liver cell bioreactor maintaining tissue monoxygenase activity and hepatospecific activities over at least 2 weeks. 2. For characterization the antihypertensive drug urapidil was used as a model compound to study maintenance of metabolic activity. Tissue-specific parameters assessed included urea and albumin secretion as well as cellular integrity. The problem of the use of serum in bioreactor cultures is addressed. 3. Bioreactor runs could be performed in serum- and lactate-free cultures with a joint recovery of oxidative biotransformation capacity for urapidil as well as tissue-specific markers. LDH release was reduced with older cultures. Fibronectin was shown as a contributing factor for cell attachment. 4. In the present study the design and function of a modular, small-scale-type bioartificial liver cell culture model is thus described lending itself for drug metabolism studies but maintaining also typical hepatospecific properties.

Endotoxin and fibrinogen degradation product-D have different actions on carbohydrate metabolism: role of Kupffer cells

The effect of endotoxin-derived lipopolysaccharide (LPS) and fibrinogen degradation product D (FDPD) on oxygen consumption and glycogenolysis in the perfused rat liver was investigated. 1. Infusion of LPS (100 micrograms/ml) or FDPD (7 micrograms/ml) caused a rapid stimulation of oxygen uptake by the perfused liver of 10-12 mumol/g/h. 2. LPS also caused a transient increase in glucose and lactate release into the perfusion medium from endogenous glycogen; however, FDPD was without effect. 3. Destruction of Kupffer cells by GdCl3 pretreatment blocked the effects of LPS and FDPD on oxygen uptake and glycogenolysis. Further, LPS and FDPD had no effect on oxygen consumption by isolated hepatocytes. Therefore, it is concluded that Kupffer cells are involved in the increase of hepatic oxygen consumption and carbohydrate release caused by LPS, most likely via release of PGE2 and PGD2. Since FDPD increased oxygen but not carbohydrate release, it is concluded that it acts via stimulating the release of mediators distinct from those released following LPS infusion.

Endotoxin inhibits glucuronidation in the liver. An effect mediated by intercellular communication

Endotoxin [lipopolysaccharide (LPS) 50 micrograms/mL] added to the perfusion medium increased glucose production and inhibited the glucuronidation of p-nitrophenol in perfused mouse liver both in recirculating and non-recirculating systems, while sulfation of p-nitrophenol was unchanged. The effects of endotoxin could be prevented by the addition of cyclooxygenase inhibitors, while PGD2 and PGE2 also caused a decrease in p-nitrophenol glucuronidation in perfused liver. In isolated hepatocytes endotoxin failed to affect p-nitrophenol conjugation, while PGD2 and PGE2 decreased the rate of it. Our results suggest that endotoxin inhibits glucuronidation through an intercellular communication presumably mediated by eicosanoids.