Effect of melatonin on the initiation and growth of mammary tumors in female rats

ABSTRACT

The effect of the pineal hormone, melatonin, on the development of mammary tumors in rats treated, with 7, 12 dimethlbenz [a] anthracene [DMBA] was investigated. Daily subcutaneous treatment of melatonin [250 micro g] into female rats, previously injected with single dose [10 mg] of DMBA, prevented the appearance of any preneoplastic lesions in 30% of rats treated for three months. Melatonin treatment for six months prevented the appearance of pathological lesions in 20% of rats. It also prevented the appearance of adenocarcinoma, in 83, 33% of treated rats. Also, the preneoplastic changes in the remaining rats were prevented and improved by different values after melatonin treatment for three and six months. In addition to preventing and modifying tumor growth, melatonin decreased significantly serum prolactin, estradiol, and progesterone in these animals. Moreover it has been shown that the effect of melatonin after six months was more marked than after three months in both tumor growth and hormonal levels especially prolactin and estradiol which were claimed to be an important factor in the development of cancer breast