Ruiz-Sanchez Esau, O'Donnell Michael J
Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1.
J Insect Physiol. 2006 Sep;52(9):920-8. doi: 10.1016/j.jinsphys.2006.05.013. Epub 2006 Jun 13.
The organic anion salicylate is a plant secondary metabolite that can protect plants against herbivores. Transport of salicylate across the basolateral membrane of the Malpighian tubules of Drosophila melanogaster was studied using a radioisotope tracer technique. The uptake of [(14)C]salicylate by the Malpighian tubules was active, saturable and Na(+)-dependent; the maximum uptake rate (J(max)) and the half saturation concentration (K(t)) were 12.6 pmoltubule(-1)min(-1) and 30.7micromoll(-1), respectively. In contrast to organic anion transport by vertebrate renal tissues, salicylate uptake was not trans-stimulated by glutarate (0.01-1.0 mmoll(-1)) or cis-inhibited by high concentrations (5 mmoll(-1)) of various alpha-keto acids (glutaric acid, alpha-ketoglutaric acid, succinic acid, and citric acid). Changes in basolateral membrane potential or physiologically relevant changes in bathing saline pH did not affect the rate of [(14)C]salicylate uptake. Ring-structure monocarboxylic acids (benzoic acid, nicotinic acid, gentisic acid, unlabelled salicylic acid, alpha-cyano-4-hydroxycinnamic acid, probenecid, fluorescein, and P-aminohippuric acid) strongly inhibited [(14)C]salicylate uptake rate. In contrast, short-chain monocarboxylic acids had little (butyric acid) or no effect (lactic acid, pyruvic acid, and propionic acid). Our results suggest that salicylate uptake across the basolateral membrane of D. melanogaster Malpighian tubules is mediated by a non-electrogenic, alpha-cyano-4-hydroxycinnamic acid-sensitive, Na(+):salicylate cotransport system.
有机阴离子水杨酸酯是一种植物次生代谢产物，能够保护植物免受食草动物侵害。利用放射性同位素示踪技术研究了水杨酸酯在黑腹果蝇马氏管基底外侧膜上的转运。马氏管对[¹⁴C]水杨酸酯的摄取是主动的、可饱和的且依赖于Na⁺；最大摄取速率（J(max)）和半饱和浓度（K(t)）分别为12.6 pmol·小管⁻¹·分钟⁻¹和30.7 μmol·L⁻¹。与脊椎动物肾组织的有机阴离子转运不同，戊二酸（0.01 - 1.0 mmol·L⁻¹）不会反刺激水杨酸酯的摄取，高浓度（5 mmol·L⁻¹）的各种α-酮酸（戊二酸、α-酮戊二酸、琥珀酸和柠檬酸）也不会顺式抑制其摄取。基底外侧膜电位的变化或生理相关的浴液pH变化不会影响[¹⁴C]水杨酸酯的摄取速率。环状结构的一元羧酸（苯甲酸、烟酸、龙胆酸、未标记的水杨酸、α-氰基-4-羟基肉桂酸、丙磺舒、荧光素和对氨基马尿酸）强烈抑制[¹⁴C]水杨酸酯的摄取速率。相比之下，短链一元羧酸几乎没有影响（丁酸）或没有影响（乳酸、丙酮酸和丙酸）。我们的结果表明，水杨酸酯在黑腹果蝇马氏管基底外侧膜上的摄取是由一种非电生性的、α-氰基-4-羟基肉桂酸敏感的Na⁺:水杨酸酯共转运系统介导的。
