Cortisol and Dexamethasone Mediate Glucocorticoid Actions in the Lesser Spotted Catshark (Scyliorhinus canicula)

Abstract

Corticosteroids are hormones produced in vertebrates exerting gluco- and mineralocorticoid actions (GC and MC) mediated by specific receptors (GR and MR, respectively). In elasmobranchs, the major circulating corticosteroid is the 1α-hydroxycorticosterone (1α-OHB). This hormone acts as a MC, but to date its role as a GC has not been established. As there is no 1α-OHB standard available, here we employed a set of in vivo and ex vivo approaches to test GC actions of other corticosteroids in the lesser spotted catshark (Scyliorhinus canicula). Dexamethasone (DEX, a synthetic corticosteroid) slow-release implants decreased plasma 1α-OHB levels after 7 days, and modified carbohydrates metabolism in liver and white muscle (energy stores and metabolic enzymes). In addition, ex vivo culture of liver and white muscle explants confirmed GC actions of corticosteroids not naturally present in sharks (cortisol and DEX) by increasing glucose secretion from these tissues. Dose–response curves induced by cortisol and DEX, altogether with the use of specific GR inhibitor mifepristone, confirmed the involvement of GR mediating glucose secretion. This study highlights the influence of corticosteroids in the glucose balance of S. canicula, though the role of 1α-OHB as a GC hormone in sharks should be further confirmed.

Los elasmobranquios (tiburones y rayas) presentan como principal corticosteroide la hormona 1α-hidroxicorticosterona (1α-OHB). Hace tiempo que se describieron sus acciones como mineralocorticoide y, aunque se sugirió que también actúa como hormona glucocorticoide, no existen pruebas concluyentes. Esto se debe a la falta de 1α-OHB purificada. En el presente estudio, y mediante el uso de corticosteroides no presentes de manera natural en los elasmobranquios (cortisol y dexametasona), se describen respuestas fisiológicas mediadas por receptores glucocortidcoides en la pintarroja (Scyliorhinus canicula). Los resultados permiten avanzar en el conocimiento de las respuestas primarias al estrés en tiburones, para mejorar el bienestar de estos animales, ya sea en cautividad o durante la captura en el medio natural.