Net Clminus flux in short-circuited skin of Rana pipiens: ouabain sensitivity and Na+ +K+ dependence

Abstract

Skin of Rama pipiens, like many other species, is considered to actively transport only Na+ when bathed in Ringer's solution on both sides. However, net Clminus influx was previously described by us in short-circuited skin of Rana pipiens, in the summer season. The skins were of low PD (5-30 mV) and high Clminus conductance. Comparison of these findings with other series indicated inverse seasonal variation between PD and Clminus conductance. It was postulated that active Clminus transport exists at all Clminus -conductance levels but at higher PD is too small to be easily detected. This report evaluates Clminus transport across skins of higher PD (and lower conductance) in winter and further characterizes the system. Net Clminus influx was demonstrated over a wide PD range under short-circuit conditions and was inversely related to the magnitude of the open-circuit PD. It was inhibited by ouabain and dependent upon Na+ in the outside medium and K+ in the inside medium. It is concluded that this is the same system present in skin of Leptodactylus ocellatus and may not he unique to these two species. It appears to be distinctly different from the acetazolamide-sensitive influx system seen in "low-Clminus" solutions in skins of numerous species. The findings are discussed in terms of (1) parallel Na+ and Clminus active transport mechanisms and (2) a neutral NaCl-pump model, recently proposed by Rehm.