Differential expression of alpha-like glutathione S-transferase (GST) isoforms in catfish intestine

Previous studies suggested that dietary composition affected glutathione S- transferase (GST) activity in catfish intestine, and this activity varied a long the intestine. In this study, catfish were fed a semi-purified diet or a commercial chow for at least 2 weeks. GST activity, percent protein cros s-reacting with anti-catfish GST pi antibody, and immuno-cross-reactivity w ith antibodies specific for human alpha, mu, pi and theta class GSTs were d etermined in cytosol prepared from sections of proximal, medial, and distal intestine. The bulk of GST activity with 1-chloro-2,4-dinitrobenzene (CDNB ) and ethacrynic acid, and the percent protein crossreacting with anti-catf ish GST pi were in the more proximal segments and dropped off distally in t he two diet groups. The percent of cross-reacting GST protein in the proxim al section of fish fed on commercial chow was significantly higher (4.3+/-1 .7%) than in fish fed purified diet (2.3+/-0.2%). Further Western blot anal ysis revealed a differential expression of GST isoforms only in the distal segment of fish fed commercial chow that recognized human anti-alpha GST an tibody. Distal intestinal segments of catfish exposed to 3,3',4,4'-tetrachl orobiphenyl (TCB) and beta -naphthoflavone (BNF) also revealed expression o f distinct alpha -like GST isoforms. Results strongly suggest the distal se gment as a site for potential biomarkers for polycyclic aromatic hydrocarbo n (PAH)- and co-planar polychlorinated biphenyl (PCB)-type contaminants. (C ) 2000 Elsevier Science Ltd. All rights reserved.