Effect of androgens on seawater adaptation in Arctic char, Salvelinus alpinus

Abstract

Sexually immature two-year old Arctic char (Salvelinus alpinus) were implanted with Silastic capsules containing testosterone or 11-ketoandrostenedione in early spring. Seawater adaptability of the hormone-treated and sham-operated fish was tested periodically from May to August using a 48h seawater challenge test with 25‰ seawater. The sham-operated control fish displayed a seasonal pattern in seawater adaptation, showing a good hypoosmoregulatory ability until mid June followed by a marked increase in plasma sodium and magnesium levels in July and August. Gill Na(+)-K(+)-ATPase activity decreased concurrently with the observed decrease in seawater adaptability. Over the same period the androgen-treated fish displayed a similar pattern in seawater adaptability, however, in May and June the plasma sodium levels were significantly higher in both androgen-treated groups compared to the control group. Plasma magnesium regulation was impaired in both androgen-treated groups in August. Gill Na(+)-K(+)-ATPase activity in the testosterone-treated fish was lower in June compared to the control fish, whereas the activity was not affected by 11-ketoandrostenedione treatment. The results show that while androgens impair the hypoosmoregulatory capacity in Arctic char, the seasonal pattern of seawater adaptability is not affected.

Seasonal changes in hypoosmoregulatory ability in landlocked and anadromous populations of Arctic charr, Salvelinus alpinus, and Atlantic salmon, Salmo salar

“…Comparing the body size at which fish were able to regulate plasma sodium at a level comparable to freshwater levels (< 170 mmol I-') revealed clear interspecific as well as interstrain differences . In anadromous The findings that landlocked Arctic charr from northern Sweden improved their seawater tolerance from May to June, followed by a marked decrease in August, agree well with earlier studies on the Hornavan strain (Schmitz 1992, Schmitz & Mayer 1993 . The landlocked and the anadromous strain from Norway showed the same seasonal pattern in seawater adaptability, but the changes occurred about one month earlier .…”

Calcium metabolism and osmoregulation during sexual maturation of river running Atlantic salmon

“…Sexual maturation, as well as treatment with sex steroids, impairs smolting of several salmonid species as indicated by a suppression of morphological smolt characteristics, gill Na + ,K + -ATPase activity and hypo-osmoregulatory ability (McCormick & Naiman, 1985;McCormick et al, 1991;Miwa & Inui, 1986;Ikuta et al, 1987;Lundqvist et al, 1989;Madsen & Korsgaard, 1989Schmitz & Mayer, 1993). However, conflicting results have been reported by Järvi et al (1991), who were unable to show any direct negative correlation between gill Na + ,K + -ATPase activity and plasma levels of androgens in pre-smolts and early mature males of Atlantic salmon.…”

Estrogenic compounds decrease growth hormone receptor abundance and alter osmoregulation in Atlantic salmon

“…During smolting, administration of sex steroids is inhibitory to the development of salinity tolerance [21,33,44,45,62]. In Atlantic salmon, administration of exogenous estradiol (E2) can compromise physiological and behavioral parameters associated with normal smolt development, such as elevated gill sodiumpotassium activated adenosine triphosphatase (Na + /K + ,-ATPase) activity, increased chloride cell or ionocyte density, and improved salinity tolerance and preference [28,29].…”