Effects of dinitrophenol on active-transport processes and cell membranes in the Malpighian tubule of Formica.
In Formica Malpighian tubules KCl secretion is driven by a V-type H+ ATPase in the luminal membrane in parallel with a H+/K+ antiporter. The effect of the protonophore dinitrophenol (DNP) was investigated on the isolated, symmetrically perfused tubule. DNP was applied in two different concentrations: 0.2 mmol/l and 1 mmol/l. The effects were fast and rapidly reversible. The equivalent short-circuit current (Isc) was reduced significantly to respectively 25 +/- 3% Cn = 4) and -3 +/- 7% (n = 11) of the control value when 0.2 mmol/l or 1 mmol/l was added to the bath. When 1 mmol/l DNP was applied the transepithelial resistance (Rte) decreased significantly to 74 +/- 11% of the control value (n = 11), and the luminal over basolateral voltage divider ratio (VDR), providing an estimate of luminal over basolateral membrane resistance, decreased to 37 +/- 12% of the control (n = 6). A concentration of 1 mmol/l DNP was also applied from the lumen. The decrease in Isc was significant, but much less pronounced (74 +/- 5% of control; n = 6) and no significant changes in Rte and VDR were observed. It is argued that, when the concentration in the bath is high enough, DNP may cross the cell and have a protonophoric effect not only on the mitochondria but also across the luminal cell membrane explaining the drop in transepithelial and in relative luminal membrane resistance.(ABSTRACT TRUNCATED AT 250 WORDS)
Fysiologie, Limburgs Universitair Centrum, Diepenbeek, Belgium.
S
S
Dijkstra
E
E
Lohrmann
E
E
Van Kerkhove
P
P
Steels
R
R
Greger
D000255:Adenosine Triphosphate / Q000037:antagonists & inhibitors*; D000818:Animals; D001000:Ants; D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism; D002463:Cell Membrane Permeability; D004140:Dinitrophenols / Q000494:pharmacology*; D017136:Ion Transport / Q000187:drug effects*; D008317:Malpighian Tubules / Q000187:drug effects* / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological
D004140:Dinitrophenols; D000255:Adenosine Triphosphate