Fluid secretion by the Drosophila Malpighian tubule

Drosophila melanogaster is a good model for studies in molecular physiology, The Malpighian (renal) tubule can be studied with classical transport physiological and electrophysiological techniques, and displays those transport specialisations that are conserved among tubules of those insects studied to date, In addition, the endocrinology of fluid secretion and the pharmacology of the second messenger control systems are both closely similar to those of other insects. At a more general level, the use of an electrogenic, proton-motive plasma membrane V-ATPase to energise secondary active transport is now know to be general to most insect, and several vertebrate, epithelia. In addition to its similarity to epithelia in a number of economically and biomedically significant organisms, D, melanogaster possesses unique advantages as an experimental model, by virtue of the sophisticated genetic tools that are available. This article summarises recent progress in two areas in which D, melanogaster has provided new insights into epithelial function: the control of epithelial fluid secretion by the nitric oxide synthase/nitric oxide/cyclic GMP signalling pathways; and the genetic analysis of the structural organisation of this tiny model, and its reconciliation with physiological properties.