Stress and cortisol treatment changed affinity and number of glucocorticoid receptors in leukocytes and gill of coho salmon.

To determine whether glucocorticoid receptors were altered during observed changes in immune function after stress or cortisol treatment, we conducted a series of experiments in which juvenile coho salmon (Oncorhynchus kisutch) were acutely or chronically stressed or fed a single meal containing cortisol. We then determined glucocorticoid receptor (GR) binding in cell-free gill preparations and whole leukocytes from spleen and anterior kidney using the synthetic hormone triamcinolone acetonide as radioligand. The affinities of GR were consistently lower in all tissues from chronically stressed fish than in tissues from controls; however, numbers of GR increased in whole leukocytes and decreased in gill. Acute stress had no affect on GR in gill and did not affect the affinity of GR in anterior kidney leukocytes, but did increase the number of GR in those leukocytes. Acute stress reduced affinity and increased numbers of GR in splenic leukocytes, suggesting heterogeneity of response to stress. Feeding cortisol to fish resulted in changes in GR from gill similar to those caused by chronic stress. Incubating leukocytes in cortisol for 3 or 24 h prior to assaying GR resulted in increased number and decreased affinity of GR in anterior kidney leukocytes, but had no effect on cells from spleen.