IMMUNOCYTOCHEMICAL AND MORPHOMETRIC STUDY ON THE CHANGES OF TSH, PRL,GH AND ACTH CELLS DURING THE DEVELOPMENT OF BUFO-ARENARUM

The development and dynamics of thyrotropin (TSH), adrenocorticotropic hormone (ACTH), prolactin (PRL), and growth hormone (GH) cells have b een studied using immunocytochemical techniques and rabbit antisera, r aised against the relevant human hormone, in the pars distalis of Bufo arenarum larvae at different stages of development. The four types of cells studied were identified in different zones of the pars distalis : TSH cells occurred mainly in the centro-ventral zone, ACTH cells in the rostral and dorsal zones, GH cells in the central and caudal zones , and PRL cells in the anterior two-thirds of the gland. This distribu tion pattern does not show significant changes with development. Morph ometry and stereology were used to evaluate the changes observed in th e volume of the pars distalis and the immunoreactive cells during deve lopment. The former increased during larval growth and decreased throu ghout the metamorphic climax. The results obtained on cell number, vol ume density, and total volume suggest that, during larval growth (pre- prometamorphosis) of B. arenarum, TSH, PRL, GH and ACTH cells show a p roliferative period with storage of their hormones; a second period in volving hormone release occurs at the metamorphic climax.