| Abstract: | Pituitary and serum levels of prolactin (PRL) and serum levels of progesterone (P) were determined by polyacrylamide gel electrophoresis and radioimmunoassays in BALB/c female mice, 15-17 or 44 weeks old, treated with chemical carcinogens. Neither 1.5 mg 3-methylcholanthrene (MCA) nor 1.5-6 mg 7,12-dimethylbenz(a)anthracene (DMBA) markedly altered pituitary or serum levels of PRL in the younger mice, though DMBA increased the total pituitary content of PRL by about 33% in the 44-week-old mice. However, this increase was not correlated with the incidence of mammary tumors in the group or individuals. MCA increased serum P levels by about 22% within 50 days of the last treatment. This increase was attributable to higher serum levels of P during the diestrous and proestrous phases of the cycle. Adrenalectomy reduced serum P levels by about 60%, wheras ovariectomy had no effect. Serum P levels in 44-week-old rats were not affected by DMBA. The results fail to support the notion that MCA and DMBA promote murine mammary tumorigenesis by increasing pituitary and serum prolactin concentrations. |
