Lack of effect of indomethacin on the growth of N-nitrosomethylurea-induced rat mammary tumors.

Elevated prostaglandin levels have been previously reported in mammary tumors. This study was designed to determine if treatment with indomethacin, a prostaglandin synthesis inhibitor, influenced the growth of N-nitrosomethylurea-induced mammary tumors in Wistar rats. Indomethacin was given in drinking water to tumor-bearing rats, and rats consumed between 2.5 and 3.0 mg/kg body weight/day. Continuous p.o. administration of indomethacin during 4 weeks did not affect the rate of tumor growth as compared to the control group of untreated rats. It can be concluded that indomethacin lack of effect on N-nitrosomethylurea-induced mammary tumors, and this may be due to a specific prostaglandin profile as compared with previous results using other experimental models.