Cortisol-induced changes in oxygen consumption and ionic regulation in coastal cutthroat trout (Oncorhynchus clarki clarki) parr

Abstract

The influence of cortisol on oxygen consumption and osmoregulatory variables was examined in coastal cutthroat trout (Oncorhynchus clarki clarki) parr kept in fresh water (FW) and transferred to seawater (SW). Intraperitoneal implants containing cortisol (50 μg g(-1)) in vegetable oil resulted in elevated plasma cortisol titres similar to those observed in fish following a 24h SW exposure. Cortisol treatment significantly increased the oxygen consumption and plasma glucose levels of trout in FW, consistent with the glucocorticoid role of cortisol. Cortisol treatment did not cause any changes in plasma ion concentrations or gill Na(+),K(+)-ATPase activity in FW after 10 days. Cortisol-implanted fish exposed to SW for 24h showed slightly improved ion regulatory ability compare to non-implanted controls. The results of this study suggest that during SW transfer in juvenile salmonids, increases in cortisol may act as both a mineralocorticoid and a glucocorticoid, depending on the developmental state of the fish (e.g., smolt versus parr). Furthermore, the relative energetic costs of osmoregulation and that of the stress associated SW transfer cannot be discerned using whole-animal oxygen consumption rates.

The effects of cortisol administration on social status and brain monoaminergic activity in rainbow troutOncorhynchus mykiss

“…One possibility is that high circulating cortisol levels affect competitive ability directly by depressing physiological condition so that fish are not able to compete effectively. Prolonged experimental administration of cortisol lowers growth rate and condition factor, and increases mortality (Barton et al, 1987;Pickering and Pottinger, 1989;Gregory and Wood, 1999), effects that have been attributed to appetite suppression, the mobilisation of energy reserves, changes in digestive tract morphology, reduced food conversion efficiency, increased metabolic rate, and immune function suppression (Barton et al, 1987;Pickering and Pottinger, 1989;Morgan and Iwama, 1996;Gregory and Wood, 1999;De Boeck et al, 2001). For example, the mean specific growth rate of cortisol-treated fish in the present study was significantly lower over the 5 day interaction period than that of the untreated fish with which they were paired, an effect that was cortisol-specific since it was eliminated by coadministration of RU486.…”

Acclimation ofS. auratato various salinities alters energy metabolism of osmoregulatory and nonosmoregulatory organs

“…Data were statistically analyzed by a one-way ANOVA test in which treatment (12,38, and 55 ppt) was the main factor and treated as a nominal independent variable. Logarithmic transformations of the data were made when necessary to fulfill the conditions of the ANOVA, but data are shown in their decimal values for clarity.…”

The significance of cortisol on acclimation to salinity in pejerrey Odontesthes bonariensis

“…In most fish, cortisol has been found to be the most important corticosteroid in the circulation, playing an important role in the osmoregulatory process (Assem and Hanke, 1981;Morgan and Iwama, 1996;Sakamoto et al, 2001), and in the respiratory and intermediary metabolism (Chan and Woo, 1978;Boon et al, 1991;Morgan and Iwama, 1996). Cortisol has been regarded as a stress-related hormone (Schreck, 1981) as well as a seawater-adapting hormone, improving the hypoosmoregulatory ability in some teleost fish (Bisbal and Specker, 1991;Hwang and Wu, 1993).…”

“…Artificial elevation of blood cortisol levels has been regarded as an effective tool to isolate the effect of stress and investigate the role of cortisol in metabolism and osmoregulation in fish (Assem and Hanke, 1981;Hwang and Wu, 1993;Specker et al, 1994). Improvement of the hypoosmoregulatory ability occurred in the coastal cutthroat trout, Oncorhynchus clarki clarki parr (Morgan and Iwama, 1996), in the Atlantic salmon Salmo salar (Bisbal and Specker, 1991) and the rainbow trout, Oncorhynchus mykiss (Madsen, 1990). Cortisol injection increased ATPase activity and reduced the increases in plasma Na + in the stenohaline common carp, Cyprinus carpio, after transfer to a salinity of 15ppt, whereas in the euryhaline tilapia, Oreochromis mossambicus (=Sarotherodon mossambicus) exposed to 27ppt, it inhibited enzyme activity and had no effect on the Na + concentration (Abo Hegab and Hanke, 1984).…”