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EVELYN M. RIVERA, Differential Responsiveness to Hormones of C3H and A Mouse Mammary Tissues in Organ Culture, Endocrinology, Volume 74, Issue 6, 1 June 1964, Pages 853–864, https://doi.org/10.1210/endo-74-6-853
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The minimal hormonal requirements for maintenance of structure and for initiation of secretion in organ cultures of prelactating mammary tissues from C3H mice were determined. The responses of strain A mice to hormonal combinations effective on C3H tissues were compared with the latter.
A minimal combination of aldosterone +insulin (1 + 5 μg/ml, respectively) permitted explant survival without inducing secretion. In C3H mammary tissues, the minimal concentrations of pituitary hormones required for initiation of secretion were influenced by parity. Prelactating lobules from parous pregnant mice were uniformly maximally stimulated by mammotropin (= prolactin, 0.5 μg/ml), or somatotropin (1 μg/ml), or mammotropin+somatotropin (0.5 μg/ml), in the presence of aldosterone +insulin (1 + 5 μg/ml, respectively). Tissues from nulliparous pregnant mice required, in addition to aldosterone+insulin (1+5 μg/ml, respectively), mammotropin (1 μg/ml), or somatotropin (2 μg/ml), or mammotropin + somatotropin (0.5 μg/ml) for uniform maximal secretion. Accordingly, the over-all effect of parity was an increase in tissue responsiveness to the secretory effects of pituitary hormones. Although some secretion could be initiated by lower concentrations of either pituitary hormone, variability in responsiveness was noted in tissues from both parous and nulliparous pregnant mice.
The differences in responsiveness between C3H and A mice were manifested in organ culture in the presence of low hormone levels. Mammary tissues from A mice were less responsive to mammotropin than were C3H tissues. The responsiveness of C3H mammary tissues and the refractoriness of A mammary tissues to the secretion-inducing effects of somatotropin suggest that somatotropin may possess intrinsic mammotropic activity, which cannot be explained solely on the basis of its contamination with mammotropin. The manifestation of the mammotropic influence of somatotropin appears to be dependent upon the genetic constitution of the responding tissue. (Endocrinology74: 853, 1964)
