Non-specific
carboxylesterases (
carboxylesterases) and
glutathione S-
transferases (
GSTs) are two groups of
drug metabolizing
enzymes responsible for hydrolysis and
glutathione conjugation of
xenobiotics. This study was conducted to determine the following: (1) the distribution of
carboxylesterase and GST activities in different rat liver cells, (2) the effects of
vitamin A deficiency (A-) on the absolute activities and on the distribution of
carboxylesterases and
GSTs in rat liver. Rat livers were fractionated into parenchymal and non-parenchymal cells by means of
collagenase perfusion and differential centrifugation. Non-parenchymal cells were further fractionated by means of
Percoll density gradient centrifugation into a layer of Kupffer cells and another layer containing stellate and endothelial cells.
Carboxylesterase and GST activities were determined in these fractions. show that: (1) both
carboxylesterases and
GSTs were mainly localized in the parenchymal fraction, (2) there was no significant difference between male and female rats with regard total activity or distribution of
carboxylesterases and
GSTs in rat liver cells, (3) A- caused a highly significant reduction in
carboxylesterase and GST activities in total liver homogenates and parenchymal cells. This reduction was not ameliorated by administration of
retinoic acid 18 hr before sacrifice of animals. These results open up a new era of investigations about the potential role of
vitamin A in the regulation of detoxification
enzymes.