Electrochemical gradients across Malpighian tubules of the house cricket, Acheta domesticus, and the mode of action of kinin and CRF-related diuretics.

摘要

Double-barrelled ion-selective microelectrodes were used to measure Na+, K+ and Cl- activities in the principal cells of cricket Malpighian tubules, allowing electrochemical gradients across apical and basal membranes to be calculated. At the basal membrane, K+ and Cl- gradients support passive exit into the bathing medium. A thermodynamic analysis shows both ions can be taken up by Na+/K+/2Cl- cotransport driven by a favourable Na+ gradient. At the apical membrane, cations are actively transported into the lumen whereas Cl- moves passively. Evidence is presented to show that diuretic kinins open an apical membrane Cl- conductance whereas Achdo-DH acts via cAMP to stimulate the basal membrane NKCC.