AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 2 432-R438, Copyright © 1994 by American Physiological Society
Downregulation of corticosteroid receptors in gills of coho salmon due to stress and cortisol treatment
J. M. Shrimpton and D. J. Randall
Department of Zoology, University of British Columbia, Vancouver, Canada.
The effect of stress and cortisol treatment on corticosteroid receptors
(CRs) in the gills of coho salmon (Oncorhynchus kisutch) was examined.
Plasma cortisol levels were elevated acutely by intraperitoneal injection
of cortisol 21-hemisuccinate and chronically by implanting miniosmotic
pumps filled with cortisol or by repeated daily handling stresses. CR
concentration and affinity were measured by radioreceptor assay employing
3H-labeled triamcinolone acetonide as ligand. Acute administration of
cortisol resulted in a reduction in CR numbers for 72 h with no change in
affinity. Chronic cortisol treatment resulted in a decrease in CR
concentration and affinity. The change in affinity occurred only while
plasma cortisol levels remained elevated, but CR population remained
significantly reduced for at least 10 days after cessation of hormone
treatment. Repeated handling stresses resulted in a similar reduction in CR
numbers but without an apparent change in affinity. The chronic or repeated
elevation in plasma cortisol downregulates the sensitivity of the gills to
cortisol by a persistent reduction in CR concentration, despite the return
to nonstress levels of circulating cortisol.
