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Daily sc injections of cholera toxin (CT; 0.1 micrograms/day), a stimulator of adenylate cyclase activity, into intact female BALB/c mice for 20 days significantly (P less than 0.05) increased mammary gland development scores from 2.0 +/- 0.1 in controls to 3.6 +/- 0.2 in CT-treated mice. Concurrent administration of 17 beta-estradiol (E; 1.0 microgram/day) and progesterone (P; 1.0 mg/day) resulted in development scores of 4.1 +/- 0.1 and 5.2 +/- 0.1 in E/P and E/P + CT treatment groups, respectively (P less than 0.05). If mice were ovariectomized before CT injection, the response to CT alone was abolished (development scores of 2.0 +/- 0.1 and 1.9 +/- 0.1 in controls and CT-treated mice, respectively). However, E/P restored the response to CT (scores of 3.2 +/- 0.2 for E/P and 4.0 +/- 0.1 for E/P + CT; P less than 0.05) in ovariectomized mice. CT significantly (P less than 0.05) increased mammary dry fat-free tissue weight from 2.89 +/- 0.41 mg (controls) to 3.78 +/- 0.37 mg (CT-treated) and from 4.03 +/- 0.59 mg (E/P-treated) to 5.42 +/- 0.91 mg (E/P + CT). Similarly, CT treatment increased mammary DNA from 138.7 +/- 11.7 micrograms (controls) to 162.8 +/- 14.4 micrograms (CT) and from 178.5 +/- 12.6 to 233.9 +/- 28.0 micrograms in the presence of E/P (P less than 0.05). Furthermore, CT was found to be mammogenic in hypophysectomized mice treated with E (1.0 microgram/day), P (1.0 mg/day), deoxycorticosterone acetate (0.5 mg/day), T4 (0.2 microgram/ml drinking water), and glucose (50 mg/ml drinking water), i.e. mammary gland development scores were 1.5 +/- 0.1 in mice treated with the above regimen and 3.1 +/- 0.1 in mice treated with the above regimen plus CT for 14 days (P less than 0.05). These results provide clear evidence, heretofore unreported, that systemic CT treatment increases mammary gland development and growth in female mice. The mammogenic effects of CT are observed in intact female mice with or without exogenous E/P, in ovariectomized mice treated with E/P, and in hypophysectomized mice treated with E/P, deoxycortisone acetate, and T4.
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