Fig. 1.

CtBP1 expression in the mouse and human pituitary. A, CtBP is localized in nuclei of cells throughout the pars anterior (PA), pars intermedia (PI), and pars nervosa (PN) of the normal mouse pituitary. B, Immunoreactivity is relatively homogeneous throughout the nuclei of almost all adenohypophyseal cells in the pars anterior and is present but weaker in the elongated nuclei of vascular endothelium (arrows). C, Double staining for CtBP (brown) and GH (red) demonstrates colocalization of nuclear CtBP and cytoplasmic GH as well as nuclear reactivity in cells that are negative for GH. The same pattern was seen in colocalization studies with other hormones. D, All but one of eight somatotroph adenomas exhibited very strong nuclear positivity in tumor cells. E, Corticotroph and lactotroph adenomas had moderate nuclear reactivity similar to that seen in the nontumorous adenohypophysis and in vascular endothelium (arrows); some lactotroph adenomas (illustrated) had focal loss of staining in scattered nuclei. F, All but one of seven null-cell adenomas were either negative or weakly positive. Vascular endothelium (arrow) served as an internal positive control.