METABOLISM OF 1-C-14-ACETATE AND 1-C-14-LEUCINE BY ANOXIC GOLDFISH (CARASSIUS-AURATUS, L) - EVIDENCE FOR ANAEROBIC LIPID-SYNTHESIS

Goldfish (Carassius auratus), acclimated to 20 degrees C and a Po-2 of 16 KPa, were subjected to environmental anoxia for a total period of 10.5 h. To determine the presence of anaerobic fatty acid synthesis, t he animals were injected intraperitoneally with 1-C-14-acetate after 3 .5 h of anoxia. The excretion of radiolabeled ethanol and CO2 was dete rmined in samples of the surrounding water. The results show that, dur ing 7 h of anoxia, 55% of the injected 1-C-14-acetate was excreted as C-14-ethanol, and 2.5% was excreted as (CO2)-C-14. The fatter indicate s TCA-cycle activity. Amino acids are important carbon donors for norm oxic fatty acid synthesis, and, because amino acid catabolism is likel y to proceed during anoxia, we investigated the production of acetyl-u nits from 1-C-14-leucine, During 7 h of anoxia, 1.8% of the injected 1 -C-14-leucine was excreted as (CO2)-C-14, which indicates that amino a cid catabolism indeed proceeds during anoxia. At the end of the exposu re, the animals; were sacrificed and the presence of radioactivity in lipids in the blood, liver, red muscle, white muscle, and peritoneal a dipose tissue was determined. About 7.5% of the injected 1-C-14-acetat e was incorporated into body lipids, mainly of the liver and red muscl e. Most of this radioactivity was present in the fatty acid portion. T he label distribution suggests that fatty acid chain elongation is the major pathway operative in anoxic goldfish.