Transport mechanisms of diuresis in Malpighian tubules of insects.

摘要: SUMMARY We have studied Malpighian tubules of Aedes aegypti using a variety methods: Ramsay fluid secretion assay, electron probe analysis of secreted fluid, in vitro microperfusion and two-electrode voltage clamp. Collectively, these methods allowed us to elucidate transepithelial transport mechanisms under control conditions the presence diuretic peptides. Mosquito natriuretic peptide (MNP), a corticotropin-releasing factor (CRF)-like peptide, selectively increases transepithelial NaCl water, meeting the loads of blood meal. The intracellular messenger MNP is cAMP, which increases the Na + conductance activates the Na /K /2Cl - -cotransporter basolateral membrane principal cells. Leucokinin non-selectively increases transepithelial KCl secretion, may deal with hemolymph volume expansions or reduce flight pay load upon eclosion from aquatic habitat. non-selective diuresis stems increase in septate junctional Cl activated by leucokinin using Ca 2+ as second messenger. Fundamental are powerful epithelial distal segment the Malpighian tubules, where rates can exceed the capacity mammalian glomerular kidneys renal turnover the extracellular compartment. In conjunction powerful epithelial transport driven V-type H -ATPase, diuretic hormones enable hematophagous probably also phytophagous insects deal with enormous dietary loads, thereby contributing evolutionary success of insects.