title: Binding of polynuclear aromatic hydrocarbons to the rat 4S cytosolic binding protein: structure-activity relationships.
abstract: The relative competitive binding affinities of benzo[a]pyrene (B[a]P), benzo[e]pyrene, benzo[g, h, i]perylene, picene, 7,12-dimethylbenz [a]anthracene, 1,2,3,4-dibenz[a]anthracene, 1,2,5,6-dibenz[a]anthracene, perylene, 4H-cyclopenta[d,e,f]-phenanthrene, benz[a] anthracene, triphenylethylene and triptycene for the rat hepatic cytosolic 4S binding protein were determined using [3H]benzo[a]pyrene as the radioligand. With the exception of triphenlethylene, triptycene and 4H-cyclopenta[d,e,f]phenanthrene, the EC50 values for the remainder of these compounds were between 1.25 X 10(-7) and 2.5 X 10(-8) M with 1,2,5,6-dibenz[a]anthracene being the most active ligand. A comparison of the relative cytosolic Ah (9S) receptor binding affinities and aryl hydrocarbon hydroxylase (AHH) induction potencies of these hydrocarbons with their 4S protein binding affinities demonstrated the following: five compounds, namely 1,2,5,6-dibenz[a]-anthracene, 1,2,3,4-dibenz[a]anthracene, picene, benzo[a]pyrene and 3-methylcholanthrene exhibited high to moderate binding affinities for the 4S and 9S cytosolic proteins (EC50 values less than 10(-6) M) and induced AHH in rat hepatoma cells; three compounds, namely perylene, benzo[e]pyrene and benzo[g,h,i]perylene exhibited high affinities for the 4S binding protein (1.25 X 10(-7), 4.4 X 10(-8) and 2.9 X 10(-8) M, respectively) and low affinities (EC50 values greater than 10(-5) M) for the Ah receptor protein; moreover these three compounds did not induce AHH in rat hepatoma H-4-II E cells in culture. These data suggest that the 4S binding protein may not play a significant role in AHH induction although the results do not rule out a function for this protein in the transregulation of AHH and its associated cytochromes P-450.
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D004790:Enzyme Induction / Q000187:drug effects; D008024:Ligands; D008297:Male; D011083:Polycyclic Compounds / Q000378:metabolism*; D051381:Rats; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D002352:Carrier Proteins; D008024:Ligands; D011083:Polycyclic Compounds; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug; D001189:Aryl Hydrocarbon Hydroxylases