EFFECTS OF ANDROGENS AND CORTISOL ON GILL ION TRANSPORTERS AND OMSMOREGULATORY CAPACITY IN ATLANTIC SALMON (SALMO SALAR)

• Sex steroids have been reported to compromise ion homeostasis in teleosts, yet there is limited and somewhat contradicting knowledge about the mechanisms through which androgens impact osmoregulatory capacity in salmonids. Immature Atlantic salmon post-smolts in seawater (SW) were injected with 11-ketoandrostenedione (OA; 25 µg/g BW), cortisol (F; 25 µg/g BW), F+OA (25 µg/g BW) and sham control (CON). After 8 days treatment, androgen treated fishdemonstrated a striking transcriptional increase in freshwater (FW)-type of ion transporters (NKA α1a ) , concurrent with no apparent ion perturbations, or down regulation of SW gill ion-transporters (NKA α1b). F treated post-smolts displayed increased gill NKA α1a transcription, with an additive effect of F+OA.. Moreover, F also resulted in decreased transcription of NKA α1b whilst fish treated with combinations of F and OA experienced severe ion perturbations and mortalities in SW, while no mortality occurred when only F was administered. Our findings suggests that androgens have, either directly or indirectly, a role in remodelling the gill epithelia for FW entry, rather than leading to osmoregulatory dysfunction in SW acclimated post-smolts. Moreover, maturing post-smolts may be sensitive to stress since combinations of elevated androgens and cortisol levels may have detrimental effects on homeostasis and fish welfare.

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NATURVETENSKAP  -- Biologi -- Zoologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Zoology (hsv//eng)

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