Selective retention of toxic polychlorinated dibenzo-p-dioxins and dibenzofurans in the liver of the rat after intravenous administration of a mixture.

A mixture of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), purified from fly ash from a municipal incinerator, was administered as a single intravenous dose to male rats. Livers were analyzed after 5 h, 1, 2, 4, 7 and 9 days for PCDD and PCDF content. Starting from t = 5 h 2,3,7,8-substituted congeners were the predominant PCDDs and PCDFs retained. 2,3,4,6,7-PnCDF was the only congener without 4 lateral chlorine atoms retained in the liver. For most of the 2,3,7,8-substituted congeners reliable half-lives could not be calculated due to the short experimental period. For only three 2,3,7,8-substituted congeners was a complete elimination from the liver found, within this time period. These congeners were 2,3,7,8-TCDF, 1,2,3,7,8- and 2,3,4,6,7-PnCDF with half-lives of less than 1, 2.1 and 1.6 days, respectively. The other PCDDs and PCDFs, without 4 lateral chlorine atoms, were not detected in the liver from 5 h to 9 days after i.v. administration. Based on the congeneric distribution patterns, it is suggested that besides metabolism, structural specific binding to the Ah-receptor and cytochrome P-450 complex might also be responsible for this selective liver retention.