We report for the first time that beta-naphthoflavone (BNF) abolishes ACTH stimulation of cortisol production in rainbow trout (Oncorhynchus mykiss). There was significantly higher hepatic cytochrome P450 content and ethoxyresorufin O-de-ethylase and uridine-5'-diphosphoglucuronic acid transferase activities in BNF-treated fish than in sham-treated controls. BNF did not significantly affect either plasma turnover or tissue distribution of [3H]cortisol-derived radioactivity. Hepatic membrane fluidity and hepatocyte capacity for cortisol uptake were not altered by BNF as compared with the sham-treated fish. These results taken together suggest that BNF does not affect cortisol-clearance mechanisms in trout. A 3 min handling disturbance period elicited a plasma cortisol response in the sham-treated fish; however, the response in the BNF-treated fish was muted and significantly lower than in the sham fish. This in vivo response corroborates the lack of interrenal sensitivity to ACTH in vitro in the BNF-treated fish, suggesting that BNF affects the ACTH pathway in trout. Our results suggest the possibility that cytochrome P450-inducing compounds may affect cortisol dynamics by decreasing interrenal responsiveness to ACTH stimulation in fish, thereby impairing the physiological responses that are necessary for the animal to cope with the stressor.

This article has been cited by other articles:

				N. Aluru and M. M. Vijayan Aryl Hydrocarbon Receptor Activation Impairs Cortisol Response to Stress in Rainbow Trout by Disrupting the Rate-Limiting Steps in Steroidogenesis Endocrinology, April 1, 2006; 147(4): 1895 - 1903. [Abstract] [Full Text] [PDF]

				N. Aluru, R. Renaud, J. F. Leatherland, and M. M. Vijayan Ah Receptor-Mediated Impairment of Interrenal Steroidogenesis Involves StAR Protein and P450scc Gene Attenuation in Rainbow Trout Toxicol. Sci., April 1, 2005; 84(2): 260 - 269. [Abstract] [Full Text] [PDF]

				N. Aluru, E. H. Jorgensen, A. G. Maule, and M. M. Vijayan PCB disruption of the hypothalamus-pituitary-interrenal axis involves brain glucocorticoid receptor downregulation in anadromous Arctic charr Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2004; 287(4): R787 - R793. [Abstract] [Full Text] [PDF]

				B. A. Barton Stress in Fishes: A Diversity of Responses with Particular Reference to Changes in Circulating Corticosteroids Integr. Comp. Biol., July 1, 2002; 42(3): 517 - 525. [Abstract] [Full Text] [PDF]