Metabolic Effects Associated with Chronically Elevated Cortisol in Rainbow Trout (Oncorhynchus mykiss)

Abstract

Carbohydrate and protein metabolism were examined in rainbow trout, Oncorhynchus mykiss, fitted with mini-osmotic pumps which maintained plasma cortisol levels at approximately 100 or 200 ng∙mL−1 for 10 d. Plasma glucose, lactate, and protein levels were unaffected by 10 d of cortisol administration, despite a significant elevation in plasma cortisol. Plasma amino acids in cortisol-treated fish (1023.8 ± 90.7 μg∙mL−1) were significantly elevated compared with shams (716.7 ± 68.5 μg∙mL−1) after 9 d. Liver glycogen content was significantly reduced by cortisol treatment. The activities of the liver enzymes assayed were unchanged; likewise the flux of radioactive substrates to radiolabeled CO2, glucose, and protein in isolated hepatocytes was unaffected in trout with chronically elevated cortisol compared with shams. The glucose replacement rate (Ra) was unchanged after 2 wk of cortisol treatment. These data do not support the purported role of cortisol as a glucocorticoid in rainbow trout. While chronically elevated cortisol may increase the supply of plasma amino acids, the hormone does not appear to alter the manner in which this potential gluconeogenic substrate is metabolized. The absence of other stressors may be partially responsible for the differences between this study and others in the literature.

Plasma biochemical responses of the planktivorous filter-feeding silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) to prolonged toxic cyanobacterial blooms in natural waters

“…The liver in fish plays an important role in several vital functions of basic metabolism, and levels of blood GLU, CHOL, and TP are generally affected by the metabolism of carbohydrate, lipid, and protein, because of hepatic damage (Andenen et al, 1992). In present study, we recorded a decrease in CHOL concentration in silver carp and decreases in both TP and CHOL concentrations in bighead carp during the blooms, indicating a possible nutritional imbalance induced by the toxic blooms.…”

Plasma biochemical responses of the omnivorous crucian carp (Carassius auratus) to crude cyanobacterial extracts

“…Pathological alterations in the blood activities of these enzymes are generally a result of hepatocyte leakage after cellular alteration or damage (Bernet et al 2001;Malbrouck et al 2006). The liver in fish plays an important role in several vital functions of basic metabolism, and levels of blood glucose (GLU), cholesterol (CHO), triglyceride (TG), and total protein (TP) are generally affected by the metabolism of carbohydrate, lipid, and protein, because of hepatic damage (Andenen et al 1992). There have been a few studies documenting alterations of these indices after intraperitoneal injection with pure microcystins (Råbergh et al 1991;Vajcová et al 1998;Beasley et al 2000).…”

The physiological stress response of salmonids: considerations for field procedures and environmental monitoring

“…Only the tricaine group displayed a transient increase in serum glucose levels at 24 h. It is interesting to note that although serum cortisol levels rose significantly for control and tricaine fish, neither group exhibited the hyperglycemia that is commonly believed to be associated with higher cortisol concentrations. Similar results were demonstrated by Andersen et al (1991) who challenged the traditional glucose-immobilizing role of cortisol.…”