Sweazea Karen L, Braun Eldon J
Department of Physiology, Arizona Health Sciences Center, University of Arizona, Tucson, Arizona 85724-5051, USA.
J Exp Zool A Comp Exp Biol. 2006 Mar 1;305(3):268-76. doi: 10.1002/jez.a.262.
Studies of prolonged avian flight have shown it to require large amounts of energy supplied mainly by free fatty acids (FFA). In the present study, the high levels of plasma ketone bodies found in sparrows (2.58 mmol l(-1)) are supportive of the use of fatty acids for flight. To determine the nature of fatty acid (oleic acid, OA) uptake, various pharmacological agents were used. The uptake of OA was examined using the extensor digitorum communis (EDC) muscle of English sparrows incubated in vitro. Initial studies demonstrated that radiolabeled OA uptake decreased in the presence of increasing unlabeled OA, suggesting that uptake occurred by a facilitative transport process. To further characterize OA uptake, EDC muscles were incubated with either: insulin (2 ng ml(-1)), insulin-like growth factor isoform-1 (IGF-I; 48 ng ml(-1)), 5'-Aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR; 2 mmol) or caffeine (5 mmol). Insulin, but not IGF-I, significantly increased OA uptake by avian EDC (P < 0.01). Caffeine and AICAR were ineffective at increasing OA uptake. A specific inhibitor of FFA transport by fatty acid transporters (FAT/CD36), sulfo-N-succinimidyl oleate (SSO; 500 micromoles), significantly decreased OA uptake at 2.5 min. The effectiveness of SSO suggests that a FAT/CD36-like protein is expressed in avian tissues. As uptake of OA was not completely blocked by SSO, it is likely that other mechanisms for FFA movement across membranes, such as diffusion, may be present.
对鸟类长时间飞行的研究表明，这需要大量主要由游离脂肪酸（FFA）提供的能量。在本研究中，麻雀血浆中高水平的酮体（2.58 mmol l(-1)）支持脂肪酸用于飞行。为了确定脂肪酸（油酸，OA）摄取的性质，使用了各种药理试剂。使用体外培养的家麻雀的趾长伸肌（EDC）来检测OA的摄取。初步研究表明，在未标记的OA增加的情况下，放射性标记的OA摄取减少，这表明摄取是通过易化转运过程发生的。为了进一步表征OA摄取，将EDC肌肉与以下物质之一一起孵育：胰岛素（2 ng ml(-1)）、胰岛素样生长因子异构体-1（IGF-I；48 ng ml(-1)）、5'-氨基咪唑-4-甲酰胺-1-β-D-呋喃核糖苷（AICAR；2 mmol）或咖啡因（5 mmol）。胰岛素而非IGF-I显著增加了鸟类EDC对OA的摄取（P < 0.01）。咖啡因和AICAR在增加OA摄取方面无效。脂肪酸转运蛋白（FAT/CD36）对FFA转运的特异性抑制剂磺基-N-琥珀酰亚胺油酸酯（SSO；500微摩尔）在2.5分钟时显著降低了OA摄取。SSO的有效性表明鸟类组织中表达了一种类似FAT/CD36的蛋白质。由于OA的摄取并未被SSO完全阻断，很可能还存在其他FFA跨膜移动的机制，如扩散。
