EFFECTS OF IONS SUBSTITUTIONS AND OF INHIBITORS ON TRANSEPITHELIAL POTENTIAL DIFFERENCE AND SODIUM FLUXES IN PERFUSED GILLS OF THE CRAB PACHYGRAPSUS-MARMORATUS
C. Pierrot et al., EFFECTS OF IONS SUBSTITUTIONS AND OF INHIBITORS ON TRANSEPITHELIAL POTENTIAL DIFFERENCE AND SODIUM FLUXES IN PERFUSED GILLS OF THE CRAB PACHYGRAPSUS-MARMORATUS, Archives of physiology and biochemistry, 103(4), 1995, pp. 466-475
With the same saline on both sides of the epithelium, a spontaneous in
side negative transepithelial potential difference (PD) was measured i
n perfused posterior gills of the euryhaline crab Pachygrapsus marmora
tus acclimated to dilute sea water. The origin of the PD and the trans
port properties of the epithelium were investigated by ionic substitut
ions and by application of inhibitors. Diffusion of Na+ and Cl- ions a
t the apical side contributes to the establishment of the PD. Sodium c
yanide (10(-2) M) added to the perfusion and incubation media almost c
ompletely inhibited the transepithelial PD and considerably decreased
the Na+ influx. Internally perfused ouabain (5.10(-3) M) halved the PD
and the Na+ influx but had no effect on the Na+ efflux. Externally ap
plied amiloride (10(-3) M) also reduced the Na+ influx by 27%. All inh
ibitions were concentration-dependent. From these results, it has been
concluded that the transepithelial PD and Na+ influx are, at least pa
rtly, generated by active, metabolic energy-requiring processes. The e
ffect of ouabain supports the existence of a Na+/K+ exchange mechanism
linked to the presence of Na+-K+ ATPase in the basolateral membrane o
f posterior gills. The effect of amiloride is discussed.