Effects of putative diuretic factors on intracellular second messenger levels in the Malpighian tubules of Aedes aegypti

Intracellular levels of the second messengers, 3',5'-cyclic adenosine monophosphate (cAMP) and inositol 1,4,5-trisphosphate (LP,) were measured in the Malpighian tubules of Aedes aegypti following the in vitro application of 5-hydroxytryptamine (5-HT) and the putative mosquito diuretic peptides, Culex salinarius diuresin and mosquito leucokinins (culekinin depolarizing peptides (CDPs) I, II, III, A. aegypti leucokinin peptides (ALPs) I, II, III). The C. salinarius diuresin significantly (p < 0.05) increased tubule intracellular cAMP concentrations. Treatment of tubules with either 5-HT or CDP-II resulted in significant increases in both intracellular cAMP and IP3 concentrations. All of the mosquito leucokinins, with the exception of CDP-I, significantly stimulated intracellular IP3 in isolated tubules. These data suggest that the mosquito leucokinins may function on the Malpighian tubules of A. aegypti by increasing the intracellular Ca2+ levels through the release of IP3 sensitive Ca2+ stores. The physiological relevance of these data to the regulation of mosquito Malpighian tubule function is discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.