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  • Title: Levels of cyclic nucleotides in autotransplanted 7, 12-dimethylbenz[a]anthracene-induced rat mammary tumors during their growth and regression.
    Author: Lee C.
    Journal: J Natl Cancer Inst; 1980 Nov; 65(5):1029-32. PubMed ID: 6253705.
    Abstract:
    Previous studies indicated that autotransplanted 7, 12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary tumors were hormone-dependent and, if derived from a single primary tumor, many of their metabolic parameters varied little. Therefore, these tumors transplanted in multiple sites provided an opportunity for serial sampling of individual tumors for repeated biochemical evaluations. In the present study, primary mammary tumors induced by DMBA in female noninbred Sprague-Dawley rats were autotransplanted at six sites. When these grafts grew to an average size of 6 cm, the hosts were ovariectomized. Eighteen days later when all tumors were apparently regressing, a silastic tubing 2 cm long containing crystalline estradiol was implanted sc into each host for 14 days. Individual tumors were serially removed from each host before ovariectomy, after ovariectomy, and after estrogen replacement. Levels of cyclic AMP (cAMP) and cyclic GMP (cGMP) in these tumors were measured by radioimmunoassay. Results indicated that tumor regression was associated with an elevation of cAMP levels and that tumor growth was accompanied by a decline in cAMP. The level of cGMP did not correlate with either tumor growth or regression. Therefore, the concept that cAMP is a biologic regulator for tissue proliferation and regression may be applied to the present model of autotransplanted, DMBA-induced rat mammary tumors.
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