Strutture cellulari e molecolari dei tubuli malpighiani coinvolte nella iono- e osmoregolazione

The paper describes urine formation in Malpighian Tubules and the principal hormonal mechanisms involved in the control of Malpighian Tubule’s function. Insect haemolymphatic pressure is equal to that present in the tubular lumen, therefore urine formation in insects relies entirely on salts active secretion. Ions secretion is driven by a V-type H+-ATPase present in the apical membrane of tubular cells. This pump generates an electrochemical potential gradient sufficient to drive Na+ and K+ fluxes from cell to lumen through H+/alkali cations exchanger. The overall Malpighian Tubules activity determines salt (KCl and NaCl) active excretion, to which water secretion is coupled. Urine formation is a complex mechanism which involves several transport proteins, many of which have been recently identified.