Abstract
Mammary tumors were induced in female Sprague-Dawley rats by giving a single oral dose of 20 mg 7,12-dimethylbenz[ a]anthracene (DMBA). Animals were killed after full development of tumors 4 months after the ingestion of DMBA. Opioid peptides in various tissues were estimated by radioimmunoassay (RIA). Tumor-bearing rats ( n = 5) had higher ( P < 0.05) contents of β-endorphin in pituitary (+60%), striatum (+52%) and midbrain (+85%) compared to animals with no tumors. However, tumor-bearing rats showed a decrease of 35% in striatal met-enkephalin content. Dynorphin level decreased ( P < 0.05) in pituitary (−49%) and hypothalamus (−29%) of tumor-bearing rats. Thus for the first time, we report the alteration in the level of these neuropeptides during the process of chemical carcinogenesis.
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