IMMUNOCYTOCHEMICAL AND MORPHOMETRIC STUDY OF TSH, PRL, GH, AND ACTH CELLS IN BUFO-ARENARUM LARVAE WITH INHIBITED THYROID-FUNCTION

Changes in the pituitary cells involved in amphibian metamorphosis wer e studied in Bufo arenarum tadpoles with inhibited thyroid function. A fter hatching, larvae were treated for 5 months with potassium perchlo rate (KClO4), a goitrogenic substance known to prevent absorption of i odine from water or food, resulting in impaired thyroid hormone synthe sis. Treated larvae continued to grow but halted their development in premetamorphosis, showing hyperplasic thyroid glands with disorganized follicles lacking colloid. Thyrotrop (TSH), lactotrop (PRL), somatotr op (GH), and corticotrop (ACTH) cells were stained immunocytochemicall y and the changes observed were evaluated morphometrically using an au tomatic image analyzer. Pars distalis volume increased in treated larv ae. Morphometric results showed that, in treated tadpoles, TSH and PRL cell populations and cell volumes increased compared to normal larvae at the same stage. Changes in the GH and ACTH cell morphometry were s light. These results indicate that in Bufo tadpoles, after chronic thy roid hormone withdrawal, TSH, PRL, GH, and ACTH cells are able to deve lop and that thyroid hormones exert a strong feedback control on the s ynthesis and storage of TSH and PRL. (C) 1995 Academic Press, Inc.