A model for fluid secretion in Rhodnius upper Malpighian tubules (UMT).
We have measured fluid secretion rate in Rhodnius prolixus upper Malpighian tubules (UMT) stimulated to secrete with 5-OH-tryptamine. We used double perfusions in order to have access separately to the basolateral and to the apical cell membranes. Thirteen pharmacological agents were applied: ouabain, Bafilomycin A(1), furosemide, bumetanide, DIOA, Probenecid, SITS, acetazolamide, amiloride, DPC, BaCl(2), pCMBS and DTT. These agents are known to block different ion transport functions, namely ATPases, co- and/or counter-transporters and ion and water channels. The basic assumption is that water movement changes reflect changes in ion transport mechanisms, which we localize as follows: (i) At the basolateral cell membrane, fundamental are a Na(+)-K(+)-2Cl(-) cotransporter and a Cl(-)-HCO(3) (-) exchanger; of intermediate importance are the Na(+)-K(+)-ATPase, Cl(-) channels and Rp-MIP water channels; K(+) channels play a lesser role: (ii) At the apical cell membrane, most important are a K(+)-Cl(-) cotransport that is being located for the first time, a V-H(+)-ATPase; and a Na(+)-H(+) exchanger; a urate-anion exchanger and K(+) channels are less important, while Cl(-) channels are not important at all. A tentative model for the function of the UMT cell is presented.
Gutiérrez
A M
AM
Instituto Venezolano de Investigaciones Científicas, IVIC, P. O. Box 21827, Caracas 1020-A, Venezuela. agutierr@ivic.ve
Hernández
C S
CS
Whittembury
G
G
D000818:Animals; D018118:Chloride Channels / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D017506:H(+)-K(+)-Exchanging ATPase / Q000378:metabolism; D017136:Ion Transport / Q000502:physiology*; D008317:Malpighian Tubules / Q000187:drug effects / Q000502:physiology*; D010042:Ouabain; D011188:Potassium / Q000378:metabolism; D012239:Rhodnius / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014867:Water / Q000378:metabolism
D018118:Chloride Channels; D002712:Chlorides; D014867:Water; D012701:Serotonin; D010042:Ouabain; D012964:Sodium; D017506:H(+)-K(+)-Exchanging ATPase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium