A 90-day subchronic toxicity study of Myrrh in F344 rats.

Myrrh is a flavoring agent and food additive. Here, we performed a subchronic toxicity study of Myrrh in male and female F344 rats by feeding at 5,000, 15,000 and 50,000 ppm for 90 days. No deaths or clinical signs were observed. Suppression of body weight gain was observed from the early phase of administration in both males and females in the 50,000 ppm group. Because there were no obvious changes in food intake in any of the Myrrh groups compared with the control group, suppression of body weight gain was considered an adverse effect of Myrrh. Hematology and serum biochemistry parameters with significant changes observed in the Myrrh groups were considered to have no toxicological significance. We observed a significant increase in relative kidney weight in male rats treated with 50,000 ppm Myrrh; this effect was considered to be related to the appearance of hyaline droplets in the epithelium of the proximal tubules histopathologically observed in this group. Immunohistochemical staining with anti-α2u-globulin antibodies suggested that these hyaline droplets were caused by factors other than α2u-globulin deposition. Thus, the no-observed-adverse-effect level of Myrrh was determined to be 15,000 ppm (males: 0.85 g/kg/day, females: 0.95 g/kg/day).