Hypercortisolemia does not affect the branchial osmoregulatory responses of the marine teleost Sparus sarba.
The effect of cortisol treatment on branchial Na(+)-K(+)-ATPase subunit mRNA abundance, enzyme activity, chloride cell number/morphometrics and serum electrolyte levels were investigated for the marine teleost Sparus sarba. Groups of fish received intraperitoneal injections of cortisol at a concentration of 4 micrograms/g body weight, daily, over a seven-day period. This dose of cortisol was sufficiently high enough to maintain a condition of hypercortisolemia as serum cortisol levels in treated fish were eleven fold higher than controls at time of sacrifice. By using branchial Na(+)-K(+)-ATPase alpha- and beta-subunit cDNA clones we were able to demonstrate that cortisol administration to S. sarba caused a significant elevation in the abundance of alpha-mRNA whereas the levels of beta-mRNA were unchanged. In addition Na(+)-K(+)-ATPase activity remained unaltered by cortisol administration. Branchial chloride cell number, exposure, apical area as well as serum Na+ and Cl- levels remained unchanged after cortisol administration. The results of this study suggest that elevated cortisol level may not necessarily translate into modulated branchial Na(+)-K(+)-ATPase activity and chloride cell function in hypo-osmoregulating marine fish.
Deane
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Department of Biology, Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China.
Kelly
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SP
Woo
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D000818:Animals; D002712:Chlorides / Q000378:metabolism; D004573:Electrolytes / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005880:Gills / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006854:Hydrocortisone / Q000097:blood / Q000494:pharmacology*; D066298:In Vitro Techniques; D010473:Perciformes / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis; D014882:Water-Electrolyte Balance / Q000187:drug effects*
D002712:Chlorides; D004573:Electrolytes; D012333:RNA, Messenger; D000254:Sodium-Potassium-Exchanging ATPase; D006854:Hydrocortisone