IMMUNOCYTOCHEMISTRY OF AMBIGUOUS CELLS IN ADULT AND EMBRYONIC DWARF (DW) MOUSE PITUITARIES

In the pars distalis of the pituitary gland in adult and embryonic dwa rf (dw/dw) mutant mice, ambiguous cells exhibiting ultrastructural fea tures common to growth hormone (GH) cells and prolactin (Prl) cells we re analyzed by means of colloidal gold ultrastructural immunocytochemi stry in order to define the functional nature of these peculiar cells. Adult and 18-day embryonic pituitaries from normal (+/+; dw/+) and dw arf (dw/dw) mice were processed with antibodies to GH, Prl, TSH (thyro id-stimulating hormone), ACTH (adrenocorticotropic hormone), LH (lutei nizing hormone), FSH (follicle-stimulating hormone), and HCG (chorioni c gonadotropic hormone). In the adult and embryonic dwarf pituitaries, the ambiguous cells reacted negatively to all of the antibodies excep t for anti-ACTH, which labeled them well. In addition, the ACTH-positi ve cells showed a much wider variety of shapes and granule size and di stribution, as compared with normal adults. In the embryos, this varia bility in ACTH cell morphology occurred not only in dwarf embryos, but in their normal counterparts as well. The results thus suggest that a dult dwarf pituitaries may retain an embryonic or incompletely differe ntiated form of ACTH cells. (C) 1993 Wiley-Liss, Inc.