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

Abstract

Hepatic AhR binding affinity for [ 3H]-2,3,7,8-tetrachlorodibenzo- p-dioxin ([ 3H]TCDD) was compared between two species widely used as laboratory animals: beagle dog and cynomolgus monkey ( Macaca fascicularis). The enriched 9S fractions from both species were obtained by sucrose gradient sedimentation. After incubation with [ 3H]TCDD, dextran-coat charcoal treatment (10 mg/ml) revealed that dog and monkey possess an AhR with a low binding affinity for [ 3H]TCDD. Saturation experiments were then achieved according to the method developed in experiments on human samples. The binding characteristics 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 [ 3H]TCDD (17.1 and 16.5 nM, respectively). The low binding affinity of dog and monkey AhRs appeared to be similar to those observed in human.