Zonation of fatty acid metabolism in rat liver.
Fatty acid metabolism was studied in periportal and perivenous hepatocytes isolated by the method of Chen & Katz [Biochem. J. (1988) 255, 99-104]. The rate of fatty acid synthesis and the activity of acetyl-CoA carboxylase were markedly enhanced in perivenous hepatocytes as compared with periportal cells. However, the response of these two parameters to short-term modulation by cellular effectors such as the hormones insulin and glucagon, the phorbol ester 4 beta-phorbol 12 beta-myristate 13 alpha-acetate and the xenobiotics ethanol and acetaldehyde was similar in the two zones of the liver. In addition, perivenous hepatocytes showed a higher capacity of esterification of exogenous fatty acids into both cellular and very-low-density-lipoprotein lipids. Nevertheless, no difference between the two cell sub-populations seemed to exist in relation to the secretion of very-low-density lipoproteins. On the other hand, the rate of fatty acid oxidation was increased in periportal cells. This could be accounted for by a higher activity of carnitine palmitoyltransferase I and a lower sensitivity of this enzyme to inhibition by malonyl-CoA in the periportal zone. No differences were observed between periportal and perivenous hepatocytes in relation to the short-term response of fatty acid oxidation and carnitine palmitoyltransferase I activity to the cellular modulators mentioned above. In conclusion, our results show that: (i) lipogenesis is achieved at higher rates in the perivenous zone of the liver, whereas the fatty-acid-oxidative process occurs with a certain preference in the periportal area of this organ; (ii) the short-term response of the different fatty-acid-metabolizing pathways to cellular effectors is quantitatively similar in the two zones of the liver.
Guzmán
M
M
Department of Biochemistry and Molecular Biology I, Faculty of Chemistry, Complutense University, Madrid, Spain.
Castro
J
J
D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000818:Animals; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D002469:Cell Separation; D004952:Esters / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D008055:Lipids / Q000096:biosynthesis; D008079:Lipoproteins, VLDL / Q000378:metabolism; D008099:Liver / Q000033:anatomy & histology / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains
D004952:Esters; D005227:Fatty Acids; D008055:Lipids; D008079:Lipoproteins, VLDL; D002334:Carnitine O-Palmitoyltransferase; D000103:Acetyl-CoA Carboxylase