The mechanism of action of the antidiuretic peptide Tenmo ADFa in Malpighian tubules of Aedes aegypti
Autor(es): Massaro, Richard C.; Lee, Lenora W.; Patel, Ankit B.; Wu, Daniel S.; Yu, Ming-Jiun; Scott, Brett N.; Schooley, David A.; Schegg, Kathleen M.; Beyenbach, Klaus W.
Resumo: The mechanism of action of Tenebrio molitor antidiuretic factor `a (Tenmo ADFa) was explored in isolated Malpighian tubules of Aedes aegypti. In the Ramsay assay of fluid secretion, Tenmo ADFa (10 super(-9) mol l super(-1)) significantly inhibited the rate of fluid secretion from 0.94 nl min super(-1) to 0.44 nl min super(-1) without significant effects on the concentrations of Na super(+), K super(+) and Cl super(-) in secreted fluid. In isolated perfused tubules, Tenmo ADFa had no effect on the transepithelial voltage (V sub(t)) and resistance (R sub(t)). In principal cells of the tubule, Tenmo ADFa had no effect on the basolateral membrane voltage (V sub(bl)) and the input resistance of principal cells (R sub(pc)). Tenmo ADFa significantly increased the intracellular concentration of cyclic guanosine monophosphate (cGMP) from 2.9 mu mol l super(-1) (control) to 7.4 mu mol l super(-1). A peritubular [cGMP] of 20 mu mol l super(-1) duplicated the antidiuretic effects of Tenmo ADFa without inducing electrophysiological effects. In contrast, 500 mu mol l super(-1) cGMP significantly depolarized V sub(bl), hyperpolarized V sub(t), and reduced R sub(t) and R sub(pc), without increasing antidiuretic potency beyond that of 20 mu mol l super(-1) cGMP. A plot of peritubular cGMP concentration vs V sub(bl) revealed a steep dose-response between 300 mu mol l super(-1) and 700 mu mol l super(-1) with an EC sub(50) of 468 mu mol l super(-1). These observations suggest a receptor- and cGMP-mediated mechanism of action of Tenmo ADFa. Tenmo ADFa and physiological concentrations of cGMP (<20 mu mol l super(-1)) reduce the rate of isosmotic fluid secretion by quenching electroneutral transport systems. The inhibition reveals that as much as 50% of the normal secretory solute and water flux can stem from electrically silent mechanisms in this highly electrogenic epithelium.
Palavras-Chave: Solutes; Secretion; Peptides; Pest control; Electrophysiology; Aquatic insects; Cyclic GMP; Malpighian tubules; Antidiuretics; Chloride; Epithelium; Tubules; Aedes aegypti; Tenebrio molitor
Imprenta: Journal of Experimental Biology, v. 207, n. 16, p. 2877-2888, 2004.
Descritores: Aedes aegypti - Cell
Data de publicação: 2004
