Lobes of rat liver respond at different rates to challenge by dietary hexachlorobenzene.

Abstract

Abstract The lobes of livers from rats fed hexachlorobenzene (HCB) develop porphyria at different rates. The caudate lobe reacts significantly slower than the median, although eventually all lobes become equally porphyric. Uroporphyrinogen decarboxylase and 5-aminolaevulinate synthetase activities are less depressed and less elevated respectively in the caudate lobe than the remainder of the liver. The variations in porphyrin levels do not appear to be due to differences in clearances of the porphyrins from the tissues. HCB levels in the lobes, although similar at the later stages of porphyria, are significantly different in the initial course of treatment. The slower reacting caudate lobe contains the highest concentrations of HCB as shown by both tissue analysis and [U-14C]HCB experiments. The differences in rate of porphyria development between median and caudate lobes cannot therefore be accounted for by differences in uptake of HCB but must reflect variations in metabolism of HCB and/or in the porphyrogenic response. Some of the possibilities have been investigated.