Androgen binding in the gills of atlantic salmon,Salmo salar, mature male parr, and immature male smolts

Abstract

In general, salmonid fishes undergo morphological, physiological, and behavioural changes, known as smoltification, before migrating out to the sea. Among these changes is an increased Na+-K+-ATPase activity in the gills that improves the hypoosmoregulatory ability. Earlier studies have shown that androgens impair the hypoosmoregulatory ability in salmonids. The aim of the present study was to investigate if this observed effect of androgens could result from a direct action at the level of the gills. To that extent, the gills of two-summer-old mature male Atlantic salmon, Salmo salar, parr or immature smolts, were homogenized and cytosolic and nuclear fractions were incubated with labelled testosterone (T) or 11-ketotestosterone (11KT) with or without unlabelled steroid added. A receptor like binding for T, but not for 11KT, was found in the cytosol and nuclei of mature male parr, with a KD of 1.3 nM in the cytosol and 3.0 nM in the nuclei. The binding of labelled T in the cytosol could be displaced with unlabelled T, 11KT, and 5α-dihydrotestosterone but no displacement of labelled T could be detected with estradiol, progesterone, cortisol, or with the antiandrogens flutamide and cyproterone acetate. No significant differences in T receptor affinity or capacity could be observed when cytosolic fractions from mature male salmon parr or immature male smolts were compared; KD of 1.1 nM, Bmax 103 fmol/mg protein and KD 1.1 nM, Bmax 75 fmol/mg protein, respectively. J. Exp. Zool. 278:391–394, 1997. © 1997 Wiley-Liss, Inc.