The effects of neonatal androgenization on mammary gland mitotic rate and susceptibility of carcinogen-induced mammary dysplastigenesis and tumorigenesis in LEW/Mai rats.

The influence of neonatal testosterone propionate treatment (androgenization) on mammary gland mitotic rate (MR) and susceptibility to 7,12-dimethylbenz(alpha)anthracene (DMBA) carcinogenesis was studied in female LEW/Mai rats. Mammary gland MR in androgenized rats was significantly lower than MR in normal rats at all ages studied. Treatment of androgenized rats with DMBA resulted in a significant increase in mammary gland MR in comparison with untreated androgenized rats. MR in DMBA-treated androgenized rats was similar to MR in DMBA-treated normal rats at most intervals after the introduction of the carcinogen. Although mammary epithelial MR in androgenized rats was significantly lower than that of normal rats of comparable age, no evidence of a decrease in susceptibility of mammary epithelium in androgenized rats to DMBA carcinogenesis was found. Instead, androgenized rats had a higher incidence of DMBA-induced mammary dysplasias, with no change in their morphologic or histologic features, than did normal rats; and there was no change in the incidence, latency, or histopathologic appearance of DMBA-induced mammary tumors in androgenized versus normal rats.