Na+ and Cl- net absorption by the isolated skin of Rana esculenta.
In the last five years, several measurements of 22Na+ influx (Ji) and outflux (Jo) across symmetrical parts of the isolated skin of Rana esculenta, under permanent short circuitation, were performed in our Institute. The mean value of the 22Na+ net fluxes (Ji-Jo) exceeded the mean value of the short circuit current measurements (1.14 +/- 0.04 versus 0.98 +/- 0.02 microE.cm-2.h-1, 253 experiments). Since this discrepancy could be due to a concomitant Cl- net absorption, 36Cl- unidirectional fluxes were detected under similar experimental conditions. The Cl- net flux mean value was 0.11 +/- 0.02 microE.cm-2.h-1 (316 experiments) which accounts for 70% of the discrepancy between the Na+ net flux and short circuit current. This Cl- net absorption occurred in the absence of electrochemical gradients and was very likely maintained by a Na+/K+/2Cl- cotransport located at the outermost membrane of the epithelium. In fact bumetanide challenge (10(-5) M in the external fluid) strongly inhibited 36Cl- influx and 22Na+ influx across this tissue and cleared off the discrepancy between short circuit current and sodium net flux.
Institute of General Physiology, University of Bari, Italy.
C
C
Lippe
V
V
Bellantuono
G
G
Cassano
C
C
Ardizzone
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002712:Chlorides / Q000493:pharmacokinetics*; D004232:Diuretics / Q000494:pharmacology; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects; D011893:Rana esculenta; D012869:Skin Absorption / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000493:pharmacokinetics*
D002712:Chlorides; D004232:Diuretics; D002034:Bumetanide; D000584:Amiloride; D012964:Sodium