Effects of phenobarbital on metabolism and toxicity of diclofenac sodium in rat hepatocytes in vitro.

Diclofenac sodium (DF-Na) was a nonsteroidal anti-inflammatory drug used in various aspects of inflammatory disease. The purpose of this study was to examine the effects of phenobarbital (PB) on metabolism and toxicity of DF-Na in vitro and explore the potential mechanism of DF-Na induced hepatotoxicity. Rat hepatocytes were isolated by a modification of the two-step in situ collagenase perfusion technique and the harvested rat hepatocytes were cultured with sandwich method. Control or PB (2 mM) pre-treated hepatocytes were incubated with DF-Na (0.1, 0.05 or 0.01 mM) in vitro and cytosolic enzyme leakage levels, cytochrome P450 (CYP) 3A activity, and metabolite content of DF-Na in cell culture medium were measured. The results showed that without any treatment hepatocyte CYP 3A activity gradually decreased with culture time. On day four, CYP 3A activity was 53% of the initial value. The decline of CYP 3A was partially reversed by CYP inducer PB, and the maximum induction of CYP 3A was 2.2-fold over control after continuous exposure of hepatocytes to 2 mM PB for 48 h. Lactic dehydrogenase (LDH), aspartate transaminase (AST), and alanine transamine (ALT) activity and the contents of the DF-Na metabolites 4'-hydroxydiclofenac (4'-OH-DF) and 5-hydroxydiclofenac (5-OH-DF) in media appeared to increase with increasing DF-Na concentrations, though there were no significant differences between DF-Na exposed and control hepatocytes. However, if the hepatocytes first were pre-treated with 2 mM PB for 2 days and then exposed to DF-Na, the concentrations of DF-Na metabolites and the activity of LDH in the media were significantly higher than that of control group. These findings suggest that the hepatotoxicity and metabolism of DF-Na in rat hepatocytes are increased when hepatic CYP 3A activity is increased.

[Study on cadmium-induced hepatocellular apoptosis in rats].

The effect of cadmium chloride on hepatocellular apoptosis in rats was studied in vivo at the doses of 5, 10 and 20 mumol/kg by using TUNEL (TdT-mediated dUTP Nick End Labelling), DNA ladder electrophoresis and flow cytometry. The results showed that TUNEL-positive cells could be detected in cadmium-treated rat liver cells. DNA fragmentation (ladder pattern) in cadmium-treated liver cells could be displayed by agarose gel electrophoresis. The rates of apoptotic cells in the liver of cadmium-treated rats at these doses were higher than those of control rats significantly. It was suggested that cadmium chloride could induce hepatocellular apoptosis of rats at certain doses in vivo.

[Study on the joint action of selenium and cadmium on DNA damage of rat liver cells].

The effect of joint action of selenium and cadmium on DNA damage in rat liver cells was investigated with single cell gel electrophoresis. The results show that both selenium and cadmium can induce DNA damage at the concentration of 8.75 mumol/L, 17.5 mumol/L and 35 mumol/L. The degree of DNA damage induced by cadmium is more serious than by selenium. When selenium and cadmium act jointly, they can antagonize each other on DNA damage at the concentration of 8.75 mumol/L and 17.5 mumol/L, but not at the concentration of 35 mumol/L. There is an antagonism between selenium and cadmium on DNA damage in rat liver cells at certain concentrations.