Co-Authors:
Rafaeli, A., Department of Entomology, Faculty of Agriculture, Hebrew University, Rehovot, Israel
Applebaum, S.W., Department of Entomology, Faculty of Agriculture, Hebrew University, Rehovot, Israel
Abstract:
Insects regulate the amount of water they excrete via their nalpighian tubules, the degree of stringency depending on the hydration of their diet and on the frequency at which they feed. The excretion of water is controlled by a diuretic hormone, which is released as required into the haemolymph by the corpora cardiaca1,2. Previous reports3-5 have shown that non-protein amino acids, known to be neurotoxic in vertebrates6 as well as in insects7, lead to a disruption of water balance in nsects. However, the exact mode of action of these amino acids has not been elucidated. We report here on preliminary experiments using isolated malpighian tubules of locusts Locusta migratoria migratorioides (R & F)) which 9 show that he non-protein amino acid L-canavanine inhibits fluid secretion in vitro by isolated tubules. Furthermore, when tubules, previously inhibited by canavanine, are subsequently stimulated by exogenous diuretic hormone (methanol extracts of storage lobes of corpora cardiaca1,2) or cyclic AMP (which mimics the action of diuretic hormone1), the stimulation obtained is much greater than that normally expected from diuretic hormone or cyclic AMP. © 1980 Nature Publishing Group.