Effect of clofibrate treatment on carnitine acyltransferases in different subcellular fractions of rat liver.
The subcellular distribution of carnitine acetyl-, octanoyl-, and palmitoyl- transferase in the livers of normal and clofibrate-treated male rats was studied with isopycnic sucrose density gradient fractionation. In normal liver 48% of total carnitine acetyltransferase activity was peroxisomal, 36% of the activity located in mitochondria and 16% in a membranous fraction containing microsomes. Carnitine octanoyltransferase and carnitine palmitoyltransferase were confined almost totally (77--81%) to mitochondria in normal liver. Clofibrate treatment increased the total activity of carnitine acetyltransferase over 30 times, whereas the total activities of the other two transferases were increased only 5-fold. From the three different subcellular carnitine acetyltransferases the mitochondrial one was most responsive to clofibrate treatment, i.e. the rise in mitochondrial activity was over 70-fold as contrasted to the 6- and 14-fold rises in peroxisomal and microsomal activities, respectively. After treatment mitochondria contained 79% of total activity. It is concluded that the clofibrate-induced increase of carnitine acetyltransferase activity is not due to the peroxisomal proliferation that occurs during clofibrate treatment. The rise in peroxisomal activity contributed only 8% to the total increase. After clofibrate treatment the greatest part of carnitine octanoyl- and palmitoyltransferase activities were located in mitochondria but a considerable amount of both activities was found also in the soluble fraction of liver.
D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D002333:Carnitine Acyltransferases / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002994:Clofibrate / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008830:Microbodies / Q000187:drug effects / Q000201:enzymology; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology; D051381:Rats; D013347:Subcellular Fractions / Q000201:enzymology
D002374:Catalase; D000217:Acyltransferases; D002333:Carnitine Acyltransferases; D002994:Clofibrate