Effect of raised serum prolactin on breast development.

The effect of serum prolactin elevation on the growth and development of the rat breast was investigated. Oral administration of the dopamine antagonist, perphenazine, led to a 5-10-fold elevation of serum prolactin after two days of treatment which was maintained for the 54 days of study. A significant (P less than 0.01) 3.4-fold increase in total breast volume was seen by Day 4 of serum prolactin elevation. Breast volume continued to rise up to Day 14 reaching an 8.9-fold peak (P less than 0.001) which was maintained for the duration of the experiment. Epithelial, myoepithelial, lumen and stromal volume changes in the ductular and alveolar compartments were quantified separately. Highly significant (P less than 0.01) volume increases were seen in all components within the first few days of prolactin elevation. Similar time courses of the growth response to elevated serum prolactin were seen in the ductal tissues reaching an approximate 3-fold peak by 7 days in duct epithelium, myoepithelium and duct stroma. Time coordinated growth responses were also seen in the alveolar tissues with larger (7-15-fold) increases in alveolar epithelium, alveolar myoepithelium and alveolar stroma, reaching a peak by 14 days.