Corticosteroid dynamics in Pacific salmon

Abstract

The tissue distribution of cortisol- 3H and - 14C and cortisone- 3H and - 14C in sexually mature and orchidectomized male sockeye salmon ( Oncorhynchus nerka) was determined at intervals after a single intraarterial injection of cortisol- 3H and cortisone- 14C. Samples of plasma, blood cells, white muscle, red muscle, liver, kidney, head kidney, spleen, gill, gut, brain, heart and, in some cases, bile, were obtained from gonadectomized fish 10, 20, 40, and 80 min after injection and from mature fish 10, 20, 40, 80, and 160 min after injection. Dichloromethane extracts of the tissues were chromatographed on thin-layer silica gel sheets and the quantity of 3H and 14C chromatographically associated with authentic cortisol and cortisone was determined by double isotope scintillation spectrometry. Cortisol and cortisone radioactivity are expressed as dpm/g tissue for a standard 1-kg fish, as a tissue: plasma ratio and as a cortisol- 3H: cortisone- 3H or cortisone- 14C: cortisol- 14C ratio. In most tisues there was a more rapid clearance of cortisol- 3H in the mature than in the gonadectomized fish. Cortisol- 3H tissue:plasma ratios were generally higher in the mature than in the gonadectomized fish. The cortisol- 3H tissue: plasma ratio was especially high in the kidney, liver, and head kidney of the mature fish. The cortisone- 14C tissue: plasma raitos were also higher in the mature than in the gonadectomized salmon but not so high as the cortisol- 3H ratios, suggesting that there are more binding sites for cortisol than for cortisone. These differences in tissue distribution explain the increase in cortisol and cortisone apparent volume of distribution noted during sexual maturation in earlier plasma clearance studies. Tissue cortisol- 3H: cortisone- 3H ratios indicate an apparent rapid conversion of cortisol to cortisone in spleen, heart, and gills in mature fish and in gut and gills in gonadectomized fish. In the liver of the gonadectomized salmon the cortisol- 3H: cortisone- 3H ratio was high and the cortisone- 14C: cortisol- 14C ratio was low, indicating a predominance of 11 keto-reductase activity. This was not the case in the mature salmon.