IMMUNOCHEMICAL IDENTIFICATION OF THYROTROPES AND GONADOTROPES IN THE PARS-DISTALIS AND PARS TUBERALIS OF THE TOAD (BUFO-BOREAS) WITH REFERENCE TO ONTOGENIC CHANGES

Morphologically distinct secretory cells in the pituitary pars distali s and pars tuberalis of larval and adult toads (Bufo boreas) immunorea ct with antiserum to the beta subunit of human thyroid-stimulating hor mone (hTSH beta). The single type of secretory cell in the pars tubera lis has sparse secretion granules uniformly smaller than those of simi larly immunoreactive cells in the pars distalis. Thyrotropin immunoact ivity appears in pars tuberalis and pars distalis before gonadotropin immunoreactivity during early development. Antisera which distinguish gonadotropes (stained with human and sea turtle LH beta) and thyrotrop es (stained with human TSH beta) as separate cell types in the pars di stalis of the adult toad immunoreact with the same single type of cell in the pars distalis of the tadpole up through metamorphosis, suggest ing the existence of a single pluripotent, glycoprotein-producing prec ursor cell early in development. Gonadotropin antisera do not react wi th the pars tuberalis in tadpoles or adults. (C) 1998 Academic Press.