Ah receptor in spleen of rodent and primate species: detection by binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin

In many species systemic toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is manifested by a generalized wasting syndrome accompanied by a variety of specific organ changes including atrophy of the thymus and spleen. TCDD toxicity in most tissues is thought to be mediated by the Ah receptor. Although the spleen is a prime target for TCDD toxicity, the possible presence of Ah receptor in the spleen has not previously been investigated. Specific binding of [3H]TCDD to Ah receptor in spleen cytosols was assessed by velocity sedimentation on sucrose gradients. Ah receptor was detected in spleen cytosols from adult Rhesus monkeys (mean +/- SEM, 36 +/- 8 fmol/mg cytosol protein), fetal Rhesus monkeys (9 +/- 6), Sprague-Dawley rats (20 +/- 5), C57BL/6J mice (18 +/- 2), New Zealand white rabbits (19 +/- 2), and Hartley guinea pigs (15 +/- 2). Ah receptor was not detectable in spleen cytosol from genetically "nonresponsive" DBA/2J mice or from Golden Syrian hamsters, a species resistant to toxicity of TCDD. Molecular properties of Ah receptor from spleen were similar to those of the receptor from liver of the same species. The high Ah receptor content in spleen cytosols from those species that are most susceptible to TCDD toxicity is consistent with the view that the Ah receptor mediates TCDD toxicity in spleen as well as in other tissues.