Relative gene expression values are reported as mRNA ALT/mRNA beta-actin. Figure 3 Effect of AG28262, a VEGR-2 inhibitor, on ALT gene expression and enzymatic activity in the caudate liver lobe. Relative gene expression values are reported as mRNA ALT/mRNA beta-actin. AG28262-induced effect on crude liver ALT enzymatic activity Both the right medial and caudate lobes demonstrated a statistical increase in ALT enzymatic activity when compared to the control with 41% (p ≤ 0.01) and 96% (p ≤ 0.01) increase respectively (Figures 1 and 3). Enzymatic ALT activity in the left lateral lobe was elevated by 29% in comparison to the control (Figure 2), but the difference was not statistically significant.

Discussion Differences in drug effects between liver lobes should be considered in toxicology evaluation of compounds. Traditional thinking regarding drug-induced hepatotoxicity commonly correlates elevated serum ALT with direct Pitavastatin in vivo hepatocellular damage. However, instances of elevated serum ALT Ruboxistaurin in the absence of microscopic evidence of hepatocellular injury do occur with some xenobiotics. This investigation was conducted to understand the ALT elevation observed with AG28262, a VEGFR-2 inhibitor, in treated rats in the absence of morphological changes in the liver. The results of this investigation suggests that the source of increased serum

ALT in AG28262 treated rats is due to an increase in gene expression rather than leakage as a result of overt hepatocellular Alanine-glyoxylate transaminase necrosis.

This study also showed a regional specific effect on ALT mRNA and protein levels within the various lobes of the liver. In an effort to rule out drug-induced hepatocellular apoptosis as a potential cause of increases in serum ALT activity, caspase 3 immunohistochemistry and TUNEL assays were used. Both assays demonstrated equivalent positive staining in the compound-treated and control rats. This information suggests that elevation in serum ALT was not due to hepatocellular apoptosis, but to an alternative mechanism. The results obtained from caspase 3 and TUNEL assays further supported the lack of morphologic hepatic changes. AG28262 treatment resulted in increased activity of ALT, AST, and ALP suggesting that AG28262 induces hepatic injury. Clinical chemistry data demonstrated a statistically significant increase in serum ALT, ALP activities, and increased (but not statistically significant) AST activity on day 8. Serum AST activity on day 8 showed individual check details variability within the compound-treated group; however there was still a remarkable elevation when compared to control animals. ALT, AST, and ALP are all enzymes found in the liver and are commonly used in conjunction to evaluate hepatic changes [8]. Despite these elevations in liver enzyme activity there were not morphological correlates within the liver. Muscle and kidney are two other sources of ALT that may contribute to the elevation in serum ALT in this study.