Regulation of chloride permeability by endogenously produced tyramine in the Drosophila Malpighian tubule.
The Malpighian (renal) tubule of Drosophila melanogaster is a useful model for studying epithelial transport. The purpose of this study was to identify factors responsible for modulating transepithelial chloride conductance in isolated tubules. I have found that tyrosine and several of its metabolites cause an increase in chloride conductance. The most potent of these agonists is tyramine, which is active at low nanomolar concentrations; the pharmacology of this response matches that of the previously published cloned insect tyramine receptor. In addition, the tubule appears capable of synthesizing tyramine from applied tyrosine, as shown by direct measurement of tyrosine decarboxylase activity. Immunohistochemical staining of tubules with an antibody against tyramine indicates that the principal cells are the sites of tyramine production, whereas previous characterization of the regulation of chloride conductance suggests that tyramine acts on the stellate cells. This is the first demonstration of a physiological role for an insect tyramine receptor.
Blumenthal
Edward M
EM
Department of Biology and Center for Biological Timing, University of Virginia, Charlottesville 22904-4328, USA. eb5f@virginia.edu
D000818:Animals; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004331:Drosophila melanogaster / Q000166:cytology / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007150:Immunohistochemistry; D017136:Ion Transport / Q000187:drug effects / Q000502:physiology*; D007684:Kidney Tubules / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D017982:Receptors, Biogenic Amine / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014439:Tyramine / Q000819:agonists / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D014443:Tyrosine / Q000819:agonists / Q000031:analogs & derivatives / Q000096:biosynthesis; D015016:Yohimbine / Q000494:pharmacology
D002712:Chlorides; D017982:Receptors, Biogenic Amine; C066175:tyramine receptor; D015016:Yohimbine; D014443:Tyrosine; D014439:Tyramine