Figure 2.

The differing proliferative responses of the ACI and COP mammary glands were reflected in mammary histology. (A and E) Thin sections from untreated ACI and COP rats, respectively. (C and G) Whole mounts from these strains. The mammary glands of untreated ACI and COP rats appeared similar and were comprised of branched ducts terminating in alveolar buds. (B and F) Thin sections from E2-treated ACI and COP rats, respectively. (D and H) Whole mounts. Although E2 treatment induced ductal branching and lobuloalveolar hyperplasia in both ACI and COP rats, the response in ACI rats was more pronounced than in COP rats.