Search

To clarify the relationship between arginine metabolism and hepatic injury, metabolomic analysis was performed in rats treated with 3 representative hepatotoxicants, monocrotaline (MCT), concanavalin A (ConA), and α-naphthyl isothiocyanate (ANIT); or a myotoxicant, tetramethyl-p-phenylenediamine (TMPD). A single dose of MCT, ConA, or ANIT dose-dependently induced hepatocellular necrosis accompanied by decreased blood arginine and increased blood alanine aminotransferase (ALT) and arginase. A close correlation was detected between arginine and ALT (r = -0.746, -0.795, -0.787 for MCT, ConA, ANIT, respectively) or between arginine and arginase (r = -0.605, -0.808, -0.672 for MCT, ConA, ANIT, respectively) in all three hepatic injury models. In contrast, neither hepatocellular necrosis nor alterations in arginine were found in the skeletal muscle injury model, although ALT was slightly increased. An in vitro assay revealed that blood samples obtained from ConA-treated rats transformed external arginine to ornithine, and the reaction was totally inhibited by an arginase inhibitor. These results suggest that blood arginase plays a crucial role in arginine metabolism associated with hepatic injury. In metabolomic analysis, nearly 450 endogenous metabolites were identified in blood obtained from all the models. Among the 13 metabolites involved in arginine metabolism, decreased arginine and increased ornithine occurred in common in the hepatic injury models, whereas citrulline and other metabolites were not altered. These results indicate that arginine metabolism, especially the arginine-to-ornithine pathway, is altered in association with acute hepatic injury. Furthermore, blood arginine and ornithine are possibly specific biomarkers for hepatic injury.

The main focus of this study was to determine the optimal administration period in terms of toxic effects on ovarian morphological changes. To assess the morphological and functional changes induced by anastrozole in ovaries, the compound was administered to female rats at dose levels or 0, 0.01, 0.1 and 50 mg/kg for 2 or 4 weeks in the repeated dose toxicity study and at levels of 0, 0.01, 0.1 and 5 mg/kg from 2 weeks prior to mating to Day 7 or pregnancy in the female fertility study. In the repeated dose toxicity study, large abnormal atretic follicles, follicular cysts, a decrease in corpus luteum and depletion of developing corpus luteum were observed in the 1 and/or 50 mg/kg groups of both the 2-week and 4-week studies in a histopathological examination of the ovaries. In the female fertility study, the pregnancy rate was decreased in the 5 mg/kg group. Irregular estrous cycles, such as an extended cycle or no cycle, were observed in the 0.1 and 5 mg/kg groups. At necropsy, decreased numbers of implantations, corpora lutea and live fetuses were noted in the 1 and/or 5 mg/kg groups. Based on these findings, histopathological changes in the ovary are important endpoints for the evaluation of drugs inducing ovarian damage. We conclude that a 2-week administration period is sufficient to detect ovarian toxicity of anastrozole in a repeated dose toxicity study.