INHIBITION OF EICOSANOID BIOSYNTHESIS MODULATES BASAL FLUID SECRETION IN THE MALPIGHIAN TUBULES OF THE YELLOW-FEVER MOSQUITO (AEDES-AEGYPTI)

Inhibition of eicosanoid biosynthesis in in vitro preparations of Malpighian tubules isolated from adult females of the yellow fever mosquito Aedes aegypti substantially reduced basal fluid secretion rates. The phospholipase A2 inhibitor 5,8,11,14-eicosatetraynoic acid (ETYA) and the cyclooxygenase inhibitor indomethacin far more effectively reduced basal fluid secretion than the epoxygenase inhibitor SKF-525A. The lipoxygenase inhibitor esculetin had no effect on basal fluid secretion. These findings indicate that products of cyclooxygenase are involved in regulating basal fluid secretion in Malpighian tubules. The effects of indomethacin were expressed in a dose-dependent manner, further indicating that eicosanoids are physiologically involved in fluid secretion. The effects of cyclooxygenase inhibition on reduction of basal secretion rates have not prevented adenosine 3',5'-cyclic monophosphate (cAMP) from exerting its secretagogue effect. These results strongly support the hypothesis that eicosanoids, especially prostaglandins, are involved in Malpighian tubule function in A. aegypti. Recognition that eicosanoids may be involved in regulating basal fluid secretion rates introduces a previously unrecognized tier of regulatory physiology into insect renal function.