Regulation of fluid secretion. Stimulates primary urine secretion by the Malpighian tubules. Increases the frequency of contraction in the heart and hindgut. Causes a dose-dependent stimulation of cAMP levels in the dorsal vessel and hindgut, but not in Malpighian tubules. Has synergistic effects on urine secretion by Malpighian tubules with serotonin. Detected throughout the central nervous system in fifth instar larvae, particularly in the medial and lateral neurosecretory cells and the dorsal unpaired median neurons of the mesothoracic ganglionic mass. Also detected in nerve processes over the salivary glands, dorsal hindgut, anterior dorsal vessel and dorsal diaphragm, and at the neurohemal sites of the abdominal nerves. Not detected in the nerves directly innervating the heart, alary muscles or posterior dorsal vessel. One hour after feeding levels on the dorsal surface of the mesothoracic ganglionic mass, the neurohemal sites and the processes above the dorsal hindgut are much reduced while background levels are increased (at protein level). Belongs to the diuretic hormone class 2 family.