[Histophysiology of the pars distalis of Tiliqua rugosa (reptilia: scincidae) and the role of the gamma cells (author's transl)].

A histological study of the pars distalis of the lizard Tiliqua rugosa following a variety of experimental treatments revealed the presence of only five cell types. Castration or ovariectomy was followed by hypertrophy and degranulation of the beta (B2) cells and, to a lesser degree, the delta cells (B1), and a slight degranulation of the gamma cells (B3), and a net activation of the thyroid gland with a slight hypertrophy of the adrenals. Systemic injections of the enzymatic inhibitor metopirone were followed by a slight involution of the beta cells and a strong hypertrophy and degranulation of the gamma cells as well as hypertrophy of the adrenal tissue. Injections of the synthetic steroid dexamethasone (which suppresses ACTH secretion by a negative feedback on the pituitary) were associated with a slight depression of the activity of the gamma cells and some regression of the adrenal glands. The alpha cells (A2) responded in an irregular manner to the same treatments but they were more often than not degranuled and/or vacuolated when compared with controls. No change in the activity of the X cells (A1) was noted with any of the treatments employed. These results suggest that the gamma cells (B3) which have for long been considered gonadotrophs secreting luteinizing hormone (LH) in reptiles, are in fact corticotrophs, and that there is only one category of gonadotrophs, the beta or B2 cells. Nonetheless, the evident temporal correlation which exists between the secretory activity of the corticotrophs and the gonadotrophs during the sexual cycle in reptiles, suggests that further study of gonad-adrenal inter-relationships should prove profitable in these animals.