Natural and estrogen-induced sexual dimorphisms in the pituitary of the newt Pleurodeles waltlii Michah and of the common frog Rana temporaria L.

In the female newt, Pleurodeles waltlii, the somatotropic cells of the adenohypophysis are characterized by large, electron-dense inclusions (1-6 micron). Inclusions were also found in adult male newts after treatment with 17-beta-estradiol (5 mg/liter of aquarium water, for 10 days to 4 months). The ultrastructural genesis of these inclusions is described for treated males and for females during sexual maturation. In both cases, the same morphological features (dimensions, and filamentous and crystalloid arrangements) have been observed. The origin of the inclusions is discussed with respect to estrogens. The effects of 17-beta-estradiol are also studied in gonadotropic pituitary cells (GTH cells) of the male frog (Rana temporaria) after injections ranging over 6 to 8 weeks (0.05 or 0.5 mg/0.1 cc PPG) every 4 days. In GTH cells, aggregates of tubules are present in large inclusions. Such aggregates are observed in GTH cells in the female frog 8 to 10 weeks after breeding. The aggregates are thought to be involved in the process of intracellular regulation of hormone secretion, since such structures appear when there is a high level of circulating estrogens.