3,3′,4,4′-Tetrachlorobiphenyl affects cortisol dynamics and hepatic function in rainbow trout

Abstract

This study investigates the impact of 3,3′,4,4′-tetrachlorobiphenyl (TCBP), a polychlorinated biphenyl (PCB) congener and cytochrome P-450 inducer, on cortisol dynamics in rainbow trout ( Oncorhynchus mykiss). Trout were given either an intraperitoneal implant of corn oil alone or corn oil containing TCBP (5 mg kg −1 body weight) and sampled 6 weeks later. TCBP-implanted fish had significantly lower condition factor and plasma glucose concentration, whereas plasma cortisol and protein, and hepatocyte protein concentration and liver ethoxyresorufin- O-deethylase (EROD) activity was significantly higher compared with the sham group. There was no significant difference in plasma lactate and amino acid concentration, hepatocyte glycogen content or liver cytosolic cortisol binding affinity or capacity between the two groups. [ 3H]Cortisol uptake was significantly higher in hepatocytes isolated from TCBP-treated fish compared with the sham fish. Also, our preliminary results suggest that the catabolism of [ 3H]cortisol by hepatocytes of TCBP-treated fish was enhanced as noted by a decrease in cortisol-specific radioactivity and an increase in tetrahydrocortisone (a cortisol metabolite) specific radioactivity. These results support a role for TCBP in enhancing cortisol clearance by hepatocytes of trout and suggest that toxicants like PCBs may impair the ability of trout to elicit a physiological response normally associated with cortisol stimulation.