Biosynthesis of cholesteryl 14-methylhexadecanoate in the liver of rats bearing transplantable tumors and during chemical carcinogenesis.
Biosynthesis of cholesteryl 14-methylhexadecanoate, cholesteryl palmitate and cholesteryl stearate was studied in the liver of rats bearing the Walker 256 carcinoma. Zajdela hepatoma and during chemical carcinogenesis following the administration of benzo[a]-pyrene. An up to 9-fold enhanced production of all these esters was found in liver homogenate during the 10--16th day after Walker tumor transplantation. Only the enzyme system esterifying cholesterol in the cytosol at pH 6.5 was stimulated while the activity of similar enzymes in mitochondria, microsomes and cytosol at an acid pH were not affected. Activity of the cytosol enzyme esterifying cholesterol at pH 6.5 was also enhanced during the active growth of Zajdela hepatoma and during the period of chemical carcinogenesis characterized by the appearance of first palpable subcutaneous tumors. Enhanced activity of cholesterol esterifying enzymes in the liver exactly coincided with periods of elevated levels of cholesteryl 14-methylhexadecanoate in the liver and blood plasma as described earlier. An increased demand of the tumor-bearing host for this cholesteryl ester utilized as a co-factor for enhanced protein synthesis is obviously met by its stimulated production in the liver tissue.
D000818:Animals; D001580:Benzopyrenes; D002279:Carcinoma 256, Walker / Q000378:metabolism; D002788:Cholesterol Esters / Q000096:biosynthesis*; D003600:Cytosol / Q000378:metabolism; D005260:Female; D008099:Liver / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism; D009374:Neoplasms, Experimental / Q000139:chemically induced / Q000378:metabolism*; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000378:metabolism; D051381:Rats
D001580:Benzopyrenes; D002788:Cholesterol Esters; D007862:Phosphatidylcholine-Sterol O-Acyltransferase