Induction of rat liver mitochondrial fatty acid elongation by the administration of peroxisome proliferator di-(2-ethylhexyl)phthalate: absence of elongation activity in peroxisomes.
The administration of di-(2-ethylhexyl)phthalate (DEHP)3 to male Sprague-Dawley rats resulted in more than a threefold increase in activity of acetyl CoA-dependent hepatic mitochondrial fatty acid elongation. Peroxisomes obtained either from control or DEHP-treated rats were not capable of elongating any of the fatty acyl CoAs tested. Furthermore, the peroxisomes possessed no trans-2-enoyl CoA reductase activity. Therefore, the elongation activity in the 7500g fraction from both control and DEHP-fed animals can be attributed totally to the mitochondria. Maximal incorporation of acetyl CoA occurred in the presence of both NADH and NADPH, and octanoyl CoA (8:0) and decanoyl CoA (10:0) were found to be optimal primers for fatty acid elongation in both control and DEHP-treated animals. The apparent Km for 8:0 CoA was 17 microM in both animal groups while the Vmax was increased from 4.5 to 12.5 nmol/min/mg following treatment. The apparent Km for 10:0 CoA was 10 microM in both control and DEHP-treated groups while the apparent Vmax increased from 2.5 to 10 nmol/min/mg; palmitoyl-CoA (16:0) was a very poor primer for chain elongation. Although the acetyl CoA-dependent fatty acid elongation was stimulated by DEHP treatment, the mitochondrial trans-2-enoyl CoA reductase activity was unaffected. The mitochondrial total elongation activity following DEHP-treatment using 8:0 CoA as primer was about two times higher than enoyl CoA reductase activity using trans-2-decenoyl CoA (10:1). This was the result of accumulation of intermediates, which were identified as trans-2-10:1 (35%), beta-hydroxy 10:0 (25%), unidentified (15%), and elongated saturated product 10:0 (24%). Elongation by one acetate unit was found in both the control and DEHP-treated animals. The results are discussed in terms of physiological significance.
D000105:Acetyl Coenzyme A / Q000494:pharmacology; D000214:Acyl Coenzyme A / Q000378:metabolism; D000818:Animals; D004051:Diethylhexyl Phthalate / Q000494:pharmacology*; D044943:Fatty Acid Desaturases / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008830:Microbodies / Q000187:drug effects / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D009243:NAD / Q000494:pharmacology; D009249:NADP / Q000494:pharmacology; D010795:Phthalic Acids / Q000494:pharmacology*; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D000214:Acyl Coenzyme A; D005227:Fatty Acids; D010795:Phthalic Acids; D011506:Proteins; D009243:NAD; C034681:octanoyl-coenzyme A; C045561:decanoyl-coenzyme A; D009249:NADP; D000105:Acetyl Coenzyme A; D004051:Diethylhexyl Phthalate; D044943:Fatty Acid Desaturases