Testosterone, 11-Ketotestosterone, and Estradiol-17β Modify Baseline and Stress-Induced Interrenal and Corticotropic Activity in Trout

Abstract

Article (refereed) -postprintPottinger, T.G.; Carrick, T.R.; Hughes, S.E.; Balm, P.H.M.. 1996 Testosterone, 11-ketotestosterone and estradiol-17β modify baseline and stress-induced interrenal and corticotropic activity in trout. General and Comparative Endocrinology, 104 (3). 284-295. 10.1006/gcen.1996.0173 Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. ABSTRACTEstradiol-17β (E), 11-ketotestosterone (KT), and testosterone (T) were administered to immature rainbow and brown trout by implantation of steroid-containing cocoa-butter pellets.This procedure elevated the levels of these hormones in the blood of the treated fish and had significant effects on plasma ACTH and cortisol levels in both unstressed and stressed rainbow trout and in stressed brown trout. E treatment significantly elevated resting levels of ACTH and cortisol and KT significantly suppressed resting ACTH levels in rainbow trout, although no effect of KT was noted on baseline cortisol levels. One hour of confinement stress increased ACTH levels in rainbow trout, but less so in T-and KT-implanted fish than in sham-implanted fish. A similar pattern was observed in stress-induced plasma cortisol levels where T and KT treatment of rainbow trout resulted in a more than 50% attenuation of plasma cortisol levels while E-implantation significantly increased stress-induced plasma cortisol levels. In brown trout subjected to confinement stress for 96h, within 1h of the onset of confinement the stress-induced increase in plasma ACTH and plasma cortisol was significantly lower in T-and KT-implanted fish than in sham-implanted controls. However, these differences were not sustained at subsequent sample points during the 96h period of continuous confinement. Nonetheless, overall mean ACTH levels for the entire confinement period were significantly enhanced in E-implanted brown trout and significantly reduced in KT-implanted fish. Overall mean cortisol levels were significantly lower in T-and KT-implanted fish. The enhancement of stress responsiveness observed in E-treated immature fish was not observed during confinement stress in untreated mature female trout, with naturally high plasma E levels. However, untreated mature male trout displayed a significantly reduced cortisol response to confinement. It is suggested that gonadal steroids are involved in the regulation of both baseline and stress-induced activity of the pituitary-interrenal axis in salmonid fish.3

Contrasting seasonal modulation of the stress response in male and female rainbow trout

“…This has been demonstrated to be an androgendependent phenomenon (Pottinger et al, 1996). In the present study it is clear that the onset of decline in responsiveness of the male fish occurs between September and October and coincides with increasing plasma 11KT levels.…”

“…Plasma T levels were also increasing in males during this period. Both androgens suppressed the ACTH and cortisol response to confinement when administered to immature rainbow trout (Pottinger et al, 1996) although 11KT was more consistent in its effects.…”

“…However, unlike mammals, in addition to high plasma levels of E2 during the reproductive period female salmonid fish also have high blood T levels (Scott & Sumpter, 1983) which may exceed levels in male fish (Scott et al, 1980). A measurement of stress-induced cortisol levels in mature female rainbow trout on a single occasion during the reproductive cycle revealed that levels of cortisol were not elevated in females compared to pre-maturational levels (Pottinger et al, 1996). This study was carried out to determine whether the stress responsiveness of female rainbow trout is modified during the reproductive cycle.…”

“…The administration of the female-specific estrogen, estradiol-17 (E2), to immature rainbow trout increased the stress-induced elevation of blood ACTH and cortisol relative to control fish (Pottinger et al, 1996) suggesting that, in common with mammals, sexually mature female salmonids may display an enhanced stress responsiveness. However, unlike mammals, in addition to high plasma levels of E2 during the reproductive period female salmonid fish also have high blood T levels (Scott & Sumpter, 1983) which may exceed levels in male fish (Scott et al, 1980).…”

Modification of the Plasma Cortisol Response to Stress in Rainbow Trout by Selective Breeding

“…The males were tested during the later part of the year (June -October), when gonadal steroid levels in maturing male rainbow trout are increasing (Scott et al, 1980). It is known that there is an androgen-dependent attenuation of stress-induced plasma cortisol levels in trout (Pottinger et al, 1995(Pottinger et al, , 1996 and this may have contributed to the lower stress-induced cortisol levels observed in the male fish.…”