Whatever your size, kidneys are the key to homeostatic regulation, continually pumping ions and water back and forth across the epithelium layer. Drosophila’s basic filtration unit is the Malpighian tubule, which is composed of two distinct cell types, stellate and principal cells. Principal cells are cation transporters that are found throughout Malpighian tubules. Stellate cells are localised to the main segment of the tubule, and had only been shown to transport chloride ions. Although visually indistinguishable, Julian Dow’s team found that principal cells are genetically heterogeneous. This led Dow to wonder whether individual principal cells were fulfilling different functions, but to test this, someone would need to make incredibly accurate measurements of tiny ion fluxes from individual cells. Enter Mark Rheault and the mighty micro-electrode!
Rheault used self-referencing ion-selective (SeRIS) microelectrodes that had been developed by teams working with Peter Smith at Woods Hole and Joe Kunkel at Amherst....
