Comp. Biochem. Physiol. Vol. 67B, pp. 593 to 597 0305-0491/80/1201-0593502.00/0 © Pergamon Press Ltd 1980. Printed in Great Britain A SURVEY OF THE NON-ESTERIFIED FATTY ACIDS AND BINDING PROTEINS IN THE PLASMAS OF SELECTED ANIMALS FLORENCE C. I. FELLOWS, F. J. R. HIRD, ROBYN M. MCLEAN and T. I. WALKER* Russell Grimwade School of Biochemistry, University of Melbourne, Parkville, Victoria, 3052, Australia (Received 5 March 1980) Abstract--1. The levels of non-esterified fatty acids (NEFA) in the plasma of a variety of animals have been estimated. 2. Only one of seven elasmobranchs contained detectable levels of NEFA. 3. The two crustaceans examined contained very low levels. 4. All the other animals contained circulating levels of a variety of NEFA ranging from 14 to 24 carbon atoms. 5. The elasmobranchs are unique in that they also do not possess proteins in the serum which bind fatty acids. INTRODUCTION It is now widely known that higher animals contain non-esterified fatty acids (NEFA) circulating in their blood in the form of dissociable complexes with serum albumin (Frederickson & Gordon, 1958). Most NEFA have their origin in adipose tissue from which they are mobilized according to the needs of tissues such as the liver, heart, kidney and red muscle which oxidize them as a source of energy. Phillips & Hird (1977) concluded that a characteristic of the liver which appeared early in evolution was the preferential oxidation of fatty acids to provide the necessary ATP for gluconeogenesis. There is, therefore, the prob- ability of an evolutionary relationship between the existence of a liver and the presence of NEFA com- bined with a protein such as serum albumin. The present paper records the measurement of NEFA and binding proteins in the plasma of a series of animals. As will be shown, the elasmobranchs examined did not fit into the expected pattern. They proved to have little or no circulating levels of NEFA and proteins which bind them. MATERIALS AND METHODS Chemicals Heptadecanoic acid, polyunsaturated fatty acid esters (PUFA No. 1, marine source and PUFA No. 2, animal source) were obtained from Supelco Inc. (Pennsylvania, U.S.A.). Butylated hydroxy-toluene, N-methyl-N-nitroso- toluene-4-sulphonamide, bovine serum albumin and Pon- ceau S were purchased from Sigma Chemical Co. Silica gel G (type 60) was from E. Merck, Darmstadt. 10% Silar-10C gas chrom Q (100-120 mesh) was obtained from Applied Science Laboratories, U.S.A. Solvents used were redistilled from AR grades. [1-14C]Oleic acid (56mCi/mmol) was obtained from the Radiochemical Centre, Amersham, * Fisheries and Wildlife Division, Ministry for Conser- vation, East Melbourne, Victoria, 3002, Australia. England. Sepraphone III was obtained from Gelman Instrument Co., U.S.A. Animals Human subjects were healthy young adults from our laboratory. Mature male rats from an inbred Buffalo strain were fed on a standard diet of Mouse Breeder Ration, Barastoc, Melbourne. Yabbies (Cherax destructor (Clark)) were obtained in the wild. Short headed lampreys (Morda- cia mordax (Richardson)) were collected from the Yarra River during the spawning migration (September- October). Cane toads (Bufo marinus (Linnaeus)) were obtained from Queensland. Axolotls (Siredon mexicanum) were bought from a local pet shop. Rainbow trout (Salmo gairdneri (Richardson)) were obtained from the Snobs Creek Hatchery, Victoria. Eastern grey kangaroos (Mac- ropus giganteus (Shaw)) were obtained in Victoria. Pigeons (Columba livia (Gmelin)) were purchased from the local market. Southern rock lobsters (Jasus novaehollandiae (Holthius)) were obtained from the Queenseliff Fishermen's Co-operative Society Limited, Victoria. Marine teleosts and elasmobranchs were collected from Port Phillip Bay and Bass Strait, Victoria. Teleosts--long-nosed flathead (Platycephalus caerulo- punctatus (McCulloch)); sand flathead (Platycephalus bas- sensis Cuvier and Valenciennes); globe fish (Atopomycterus nicthemerus (Cuvier)); long snouted boarfish (Pentaceropsis recurvirostris (Richardson)). Elasmobranchs--white-spotted stingaree (Urolophus paucimaculatus (Dixon)); common stingaree (Urolophus tes- taceus (Mueller and Henle)); eagle ray (Myliobatis australis Macleay); southern fiddler (Trygonorhinafasciata guanerius Whitley); Melbourne skate (Raja whitleyi Iredale); Port Jackson shark (Heterodontus portusjacksoni (Meyer)); draughtboard shark (Cephaloscyllium isabella laticeps (Dumeril)). Blood samples All animals were starved for 24--48 hr before taking the blood samples with the exception of the teleosts, elasmo- branchs and crustaceans which were not starved. The blood samples were mixed with EDTA (20#1 0.2 M/ml blood) and anti-oxidant (butylated hydroxy-toluene 593