Effect of estradiol on apoptosis, proliferation and steroidogenic enzymes in the testes of the toad Rhinella arenarum (Amphibia, Anura).

Fil: Regueira, Eleonora. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biologia Experimental. Laboratorio de Endocrinologia Comparada; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Seasonal changes and regulation of the glucocorticoid receptor in the testis of the toad Rhinella arenarum.

Estradiol and reproduction in the South American toad Rhinella arenarum (Amphibian, Anura).

In rat Leydig cells, glucocorticoids (GCs) inhibit testosterone production through the interaction with the glucocorticoid receptor (GR). However, the sensitivity of those cells to GCs is regulated by the enzyme 11β-hydroxysteroid dehydrogenase Type 1 (11β-HSD1). In the testes of the toad Rhinella arenarum, the presence of an 11β-HSD similar to type 2 and a cytosolic GR has also been described. However, there is a lack of information regarding the effects of GCs on amphibian testicular steroidogenesis. In this study, the effects of corticosterone on androgen production, and the activity of two steroidogenic enzymes in toad testes were reported. Corticosterone inhibits androgen production via the GR because the GR antagonist RU486 prevents corticosterone-induced inhibition of testosterone. Corticosterone also reduced the activity of the cytochrome P450 17-hydroxylase, C17,20-lyase (Cyp450 c17) without affecting the 3β-hydroxysteroid dehydrogenase/isomerase activity. This effect on Cyp450 c17 was likewise inhibited by RU486. On the other hand, corticosterone had no effect on the amount of steroidogenic acute regulator protein. These results suggest that GCs inhibit steroidogenesis in toad testes by reducing of Cyp450 c17 activity via a GR-mediated mechanism. © 2018 Wiley Periodicals, Inc.

Effect of glucocorticoids on androgen biosynthesis in the testes of the toad Rhinella arenarum (Amphibia, Anura).

Non-mammalian vertebrates do not exhibit the anatomical cortex-medullary relationship like mammals for the homologous adrenocortical cells and chromaffin cells. However, there is a general trend for a closer anatomical relationship between these tissues from being entirely separate in ancient fishes with direct associations with the kidneys to the evolution of discrete, separate glands in reptiles and birds. The synthesis of corticosteroids is the same as in mammals with the exception of elasmobranchs that produce a unique corticosteroid, 1α-hydroxycorticosterone. Teleosts rely on cortisol as the principal mineralocorticoid and glucocorticoid. Amphibians, reptiles, and birds secrete corticosterone and aldosterone as their glucocorticoid and mineralocorticoid, respectively. Some larval and aquatic amphibians, however, rely on cortisol. The role in non-mammals for cortisol and corticosterone in gluconeogenesis, the stress response, and aging are similar to those of mammals. Aldosterone secretion is regulated by a renin-angiotensin system in non-mammalian tetrapods. Blood pressure regulation involves the renin-angiotensin system in non-mammals similar to that of mammals and natriuretic peptides antagonize Ang-II actions. Chromaffin cells participate in emergency reactions and stress responses as described for mammals. In non-mammals, chromaffin cells generally secrete more norepinephrine than epinephrine. Clearly, cells of non-mammals have the capacity to convert norepinephrine to epinephrine, indicating that this biosynthetic step is phylogenetically ancient.

Luis Fabián Canosa

Papers

5α-Reductase, an enzyme regulating glucocorticoid action in the testis of Rhinella arenarum (Amphibia: Anura).