Effect of IGF-I gene therapy on lactotropic cells of pituitary adenomas. Representative fields of specifically immunostained PRL-cells in the pituitary gland of an intact (Intact) rat, an animal treated with estrogen for 4 weeks (E only), and animal receiving estrogen for 4 weeks and RAd-GFP during the last experimental week (E + RAdGFP) and an animal receiving estrogen for 4 weeks and RAd-IGF-I during the last experimental week (E + RAd-IGF-I). Insets. Higher magnification views of the specimens. EnVision system peroxidase. Bar: 25 μm. Inset: 12.5 μm.