Cell types of the pars distalis: seasonal changes in secretory activity and effect of steroids on spermatogenesis in Rana hexadactyla.

: Cytomorphological features and tinctorial affinities of the adenohypophyseal gonadotrophs have been studied in stained preparations of the pituitary of adult male frogs Rana hexadactyla Lesson, at monthly intervals during a calendar year. All the five morphologically distinct cell types showed a progressive increase in size from August of February, followed by a decrease from March to July. Extrusion of the synthetized product occurred in the summer and during this period production was low. Injection of steroids viz. stilboestrol, testosterone, oestradiol, doca and cortisol, interfered with the elaboration and secretion of gonadotropins, the adenohypophyseal feedback mechanism, and the sensitivity of the germinal epithelium. Changes in gonadotropins secretion and their impact on the testis are discussed.