Physiological stress responses including free and protein-bound cortisol in two strains of rainbow trout

Author

Colleen Caldwell Woodward

Date of Award

6-1988

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major Professor

Richard J. Strange

Committee Members

Hank G. Kattesh, Neil Greenberg, Tom Chen, J. Larry Wilson

Abstract

The stress induced changes in plasma cortisol, glucose, and chloride were more extreme in wild rainbow trout (Salmo gairdneri) than in hatchery-reared rainbow trout subjected to severe short-term confinement in a net and electroshock. By 12 h of net confinement, plasma cortisol in wild fish increased from resting levels of 10 ng/mL to A80 ng/mL compared to hatchery-reared fish which increased from resting levels of 2 ng/mL to 155 ng/mL. Plasma glucose was higher in wild fish, increasing from resting levels of 55 mg/dL to 284 mg/dL compared to the increase in hatchery-reared fish from resting levels of 58 mg/dL to 196 mg/dL. Plasma concentrations of cortisol, glucose, and chloride were less altered in response to electroshock than they were in response to net confinement. One hour after galvano-narcosis, plasma cortisol concentrations in the wild fish peaked at 234 ng/mL and remained moderately elevated for 4 d; cortisol in hatchery-reared fish peaked at 70 ng/mL within 0.5 h of the electrical stimulus and then returned to resting levels within 1 h. No substantial changes in plasma glucose or plasma chloride occurred in either strain after galvanonarcosis.

Except for the initial disturbances, stress-induced changes in plasma cortisol, glucose, and chloride were only slightly varied throughout six weeks of long-term, moderate confinement for both strains. Distribution of plasma cortisol bound to a heat-labile carrier protein (corticosteroid binding-protein (CBP)) in both strains ranged iv from 5 to 10% at prestress conditions. Cortisol bound to CBP increased to 32% in the wild fish and to 28% in the hatchery-reared fish by the end of confinement; however, CBP in control hatchery-reared fish increased throughout the study. The distribution of plasma cortisol bound to a non heat-labile protein (albumin protein (Alb-P)) in both strains ranged from 35 to A5 % at prestress conditions, and fluctuated from 26 to 60 % throughout the confinement. The ratio of free to total cortisol concentration for both strains indicates that free cortisol is consistently and slightly less than one-half of total cortisol throughout the normal physiological range.

Recommended Citation

Woodward, Colleen Caldwell, "Physiological stress responses including free and protein-bound cortisol in two strains of rainbow trout. " PhD diss., University of Tennessee, 1988.
https://trace.tennessee.edu/utk_graddiss/11994