FLUID TRANSPORT IN CALLIPHORA MALPIGHIAN TUBULES - DIURETIC HORMONE FROM THE THORACIC GANGLION AND ABDOMINAL NERVES

The rate of fluid secretion in vitro by Malpighian tubules of 3-day-old adult blowflies (Calliphora vicina) is increased by more than 8 times when exposed to an extract of the fly's thoracic ganglion and abdominal nerves. Smaller amounts of stimulatory activity are also retrievable from other body tissues: some activity is present in the brain, but other tissue activity is consistent with the presence of the stimulatory factor in fine branches of the abdominal nerves. It is suggested that this factor is a diuretic hormone. Maximal stimulation of fluid secretion is achieved within 2-3 min of exposure to the hormone, but the rate of secretion decays only slowly when the hormone is removed (t 1 2 = approx. 35 min). The hormone is stable to boiling and freezing, and enzyme experiments suggest it is a polypeptide. The hormone is inactivated when incubated in the presence of haemolymph, but the Malpighian tubules themselves do not appear to break down or excrete the hormone. © 1979.