Patterns of cyclic AMP binding in normal human breast.

Cyclic AMP binding proteins have been measured in normal breast tissue, in a variety of physiological conditions including resting state (69 cases), pregnancy (15 cases), lactation (4 cases), post-lactational involution (6 cases), and prolonged involution (10 cases). Levels varied greatly within the groups but median values were elevated in pregnancy, lactation, and post-lactational involution as compared with the resting and prolonged involutionary states. The proportion of different types of cyclic AMP binding proteins also differed between groups. Resting breast showed approximately equal amounts of type I and II whereas pregnant and postlactational involuting breast tissue had an increased proportion of type I binding, and the prolonged involutionary state tended to be associated with low type I. Within the subgroup of nulliparous resting breasts, the proportion of type I cyclic AMP binding protein was significantly elevated during the second half of the menstrual cycle compared with the first (p < 0.05). There were also significant positive associations between the level of epithelial proliferation and both total (p < 0.015) and type I (p < 0.002) cyclic AMP binding. This represents the strongest of association thus far reported between signalling systems and proliferation in the normal breast.