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

Abstract

Leukocytes from spleen and anterior kidney of both juvenile chinook salmon ( Oncorhynchus tshawytscha) and rainbow trout ( O. mykiss) demonstrated specific binding of 3H-testosterone and the synthetic androgen 3H-mibolerone. Saturation analysis of leukocytes from anterior kidney of rainbow trout using 3H-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 3H-mibolerone could be displaced by the natural androgens testosterone and 11-ketotestosterone and by the synthetic androgens mibolerone and 17 α-methyltestosterone, while even 500-fold excess of the known immunosuppressive steroid cortisol did not displace specifically bound 3H-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 17α-methyltestosterone) all significantly reduced the number of antibody producing cells in in vitro cultures of chinook salmon anterior kidney leukocytes.