Fig. 3.

Severe hypoplasia of the anterior pituitary lobe in adult Pact^−/− mice. Adult pituitaries from female littermates Pact^+/+ (A and C) or Pact^−/− mice (B and D) were examined at P90. (A) and (B) are light micrographs showing the pituitary (pit), which lies perpendicular between the 2 trigeminal nerves (tg) on the base of the skull. C and D are H&E-stained sections of pituitary. p, posterior lobe; i, intermediate lobe; a, anterior lobe. When normalized to body size, Pact^−/− mice have normal sized posterior and intermediate lobes, but a severely reduced anterior lobe. All anterior pituitary lobe cell lineages are present in Pact^−/− mice. Immunohistochemistry of pituitaries from Pact^+/+ (E, G, I, K, and M) and Pact^−/− (F, H, J, L, and N) mice. (E and F) Prolactin (lactotrophs); (G and H) Growth Hormone (somatotrophs). (I and J) Luteinizing Hormone, (gonadotrophs); (K and L) Thyroid-stimulating Hormone, (thyrotrophs); (M and N) Adrenocorticotophic hormone (corticotrophs). (O) Hypoplasia in adult Pact^−/− mice is more pronounced in the lactotroph population, and the percentage of thyrotrophs is increased. The percentage of cells expressing each hormone per DAPI-stained cell is shown. Hormone-positive/DAPI-positive averages were determined from counting multiple sections from each mouse; error bars, SEM. * = P < 0.05, ** = P < 0.005, Pact^+/+ vs. Pact^−/− mice. The number of animals represented for each hormone are indicated for Wt and ko, respectively: ACTH: n = 5, 6; LH: n = 4, 5; GH: n = 6, 6; PRL: n = 6, 7; and TSH: n = 5, 5. An average of 8,300 cells were counted for each hormone per genotype.