Hepatic Ah receptor binding affinity for 2,3,7,8-tetrachlorodibenzo-p-dioxin: similarity between beagle dog and cynomolgus monkey

Hepatic AhR binding affinity for [H-3] 2,3,7,8-tetrachlorodibenzo-p-dioxin ([H-3]TCDD) was compared between two species widely used as laboratory anim als: beagle dog and cynomolgus monkey (Macaca fascicularis). The enriched 9 S fractions from both species were obtained by sucrose gradient sedimentati on. After incubation with [H-3]TCDD, dextran-coat charcoal treatment (10 mg /ml) revealed that dog and monkey possess an AhR with a low binding affinit y for [H-3]TCDD. Saturation experiments were then achieved according to the method developed in experiments on human samples. The binding characterist ics were determined after analysis of the data by Scatchard and Woolf plots . Receptor concentrations were quite similar in dog and monkey liver (26.6 and 14.4 pmol/mg, respectively) as well as the affinity (K-d) for [H-3]TCDD (17.1 and 16.5 nM, respectively). The low binding affinity of dog and monk ey AhRs appeared to be similar to those observed in human. (C) 1999 Elsevie r Science ireland Ltd. All rights reserved.