Ultrastructural immunocytochemistry of somatotrophs and mammotrophs in embryos of the dwarf mutant mouse.

The embryonic development of somatotrophs and mammotrophs in the adenohypophysis in dwarf (dw) mutant mice was studied by means of ultrastructural immunocytochemistry. Embryos at 16-18 days of gestation were removed from litters consisting entirely of dwarf homozygotes obtained from homozygous matings of adult dwarfs in which reproductivity was induced by means of hormone supplementation and renal capsule implants of normal pituitaries. Litters from normal (+/+) matings served as controls. Pituitaries from adult normal and dwarf mice also were removed and processed with the embryonic material. Thin sections were exposed to anti-growth-hormone serum (anti-GH) or to antiprolactin serum (anti-PRL) and processed immunocytochemically with the colloidal gold procedure. In the normal pituitaries, a strong positive reaction to anti-GH occurred in the adult and in embryos as early as 16 days, whereas the reaction to anti-PRL was strong in the adults but relatively weak in the embryos. In dwarf embryonic and adult pituitaries, ambiguous cells showing combinations of features characteristic of somatotrophs and mammotrophs were present. However, neither these cells nor other granulated cells reacted to anti-GH or to anti-PRL, except for a questionable reaction to the latter at 18 days and in the adult. Thus, the dwarf pituitary shows functional as well as morphological abnormalities as early as 16 days of gestation.