1‐¹⁴C‐Linoleic acid distribution in various tissue lipids of guinea pigs following an oral dose

Abstract

A recent study on the metabolism of 1‐14C‐α‐linolenic acid in the guinea pig revealed that the fur had the highest specific activity of all tissues examined, 48 h after dosing. The present study investigated the pattern of tissue lipid labeling following an oral dose of 1‐14C‐linoleic acid after the animals had been dosed for the same time as above. Guinea pigs were fed one of two diets with a constant linoleic acid content (18% total fatty acids) and a different content of α‐linolenic acid (0.3 or 17.3%) from weaning for 3 wk and 1‐14C‐linoleic acid was given orally to each animal for 48 h prior to sacrifice. The most highly labeled tissues (dpm/mg of linoleic acid) were liver, followed by brain, lung and spleen, heart, kidney and adrenal and intestines, in both diet groups. The liver had almost a three‐fold higher specific activity than skin and fur which was more extensively labeled than the adipose and carcass. Approximately two‐thirds of the label in skin plus fur was found in the fur which, because of a low lipid mass, would indicate that the fur was highly labeled. All tissues derived from animals on the diet with the low α‐linolenic acid level were significantly more labeled than the tissues from the animals on the high α‐linolenic acid diet, by a factor of 1.5 to 3. The phospholipid fraction was the most highly labeled fraction in the liver, free fatty acids were the most labeled fraction in skin & fur, while triacyglycerols were the most labeled in the carcass and adipose tissue. In these tissues, more than 90% of the radioactivity was found in fatty acids with 2‐double bonds in the tissue lipids. These data indicate that the majority of label found in guinea pig tissues 48 h after dosing was still associated with a fatty acid fraction with 2‐double bonds, which suggests there was little metabolism of linoleic acid to more highly unsaturated fatty acids in this time frame. In this study, the labeling of guinea pig tissues with linoleic acid, 48 h after dosing, was quite different from the labeling with α‐linolenic acid reported previously. The retention of the administered radioactivity from 14C‐linoleic acid in the whole body lipids was 1.6 times higher in the group fed the low α‐linolenic acid diet (diet contained a total of 1.8 g PUFA/100 g diet)compared with the group fed the high α‐linolenic acid diet (diet contained 3.6 g PUFA/100 g diet). The lack of retention of 14C‐labeled lipids in the whole body would be consistent with an increased rate of β‐oxidation of the labeled fatty acid on the diet rich in PUFA, a result supported by other studies using direct measurement of labeled carbon dioxide.

Ethyl arachidonate is the predominant fatty acid ethyl ester in the brains of alcohol‐intoxicated subjects at autopsy

“…The rapid turnover of arachidonate from these molecular species may be related to the increased availability of arachidonate for FAEE synthesis. Finally, there is a report by Fu et al (16) in which guinea pigs received an oral dose of radiolabeled linoleate, and the distribution of its metabolites in various tissue lipids was followed. In these studies, there was much more arachidonate than linoleate in the brain of the guinea pigs (16).…”

“…Finally, there is a report by Fu et al (16) in which guinea pigs received an oral dose of radiolabeled linoleate, and the distribution of its metabolites in various tissue lipids was followed. In these studies, there was much more arachidonate than linoleate in the brain of the guinea pigs (16). Other reports also have indicated that there is a significant preponderance of arachidonate relative to the linoleate in the brain (17,18).…”

Distribution of omega-6 and omega-3 polyunsaturated fatty acids in the whole rat body and 25 compartments

“…It has long been appreciated that particular PUFAs are selectively concentrated in particular organs and tissues, some examples being linoleic acid enrichment in liver [6, 7], α-linolenic acid enrichment in skin and fur [8], docosahaexenoic acid (DHA) in brain [9], and n-6 docosapentaenoic acid (DPAn-6) in testes [10]. Many studies have described PUFA profiles in major organs in young rats [11] such as, rat blood, muscle and some viscera [12], as well as autopsy studies in human subjects [13].…”

Sebaceous Lipids

“…Sebum analysis demonstrates that these dietary essential fatty acids and their derivatives constitute small amounts in surface lipid samplings (Nicolaides 1974). Not long ago, two intriguing studies that took place in the beginning of this millennium (Fu and Sinclair 2000;Fu et al 2001), revealed a tight association of these essential fatty acids with the skin. When guinea pigs were dosed with radioactively labeled linoleic and linolenic acids, their skin and fur became the most heavily labeled tissue, via the action of the sebaceous glands, suggesting an essential role for essential fatty acids in sebaceous and skin biology.…”