Androgens and immunocompetence in salmonids: Specific binding in and reduced immunocompetence of salmonid lymphocytes exposed to natural and synthetic androgens

Leukocytes from spleen and anterior kidney of both juvenile chinook salmon (Oncorhynchus tshawytscha) and rainbow trout (O. mykiss) demonstrated specific binding of H-3-testosterone and the synthetic androgen H-3-mibolerone. Saturation analysis of leukocytes from anterior kidney of rainbow trout using H-3-mibolerone indicated a single class of high affinity binding sites with K-d = 1.04 nM +/- 0.31 nM and B-max = 0.11 nM +/- 0.01 nM. Specific binding of H-3-mibolerone could be displaced by the natural androgens testosterone and 11-ketotestosterone and by the synthetic androgens mibolerone and 17 alpha-methyltestosterone, while even 500-fold excess of the known immunosuppressive steroid cortisol did not displace specifically bound H-3-mibolerone. A link between these steroid binding sites and androgen induced immunosuppression is indicated by the fact that the androgens which demonstrated specificity for the binding sites (testosterone, mibolerone and 17 alpha-methyltestosterone) all significantly reduced the number of antibody producing cells in in vitro cultures of chinook salmon anterior kidney leukocytes.