Net CI − flux in short-circuited skin of Rana pipiens: Ouabain sensitivity and [formula omitted] dependence

Abstract

Skin of Rana pipiens, like many other species, is considered to actively trassport only Na + when bathed in Ringer's solution on both sides. However, net CI − 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 CI − conductance. Comparison of these findings with other series indicated inverse seasonal variation between PD and CI − conductance. It was postulated that active CI − transport exists at all CI −-conductance levels but at higher PD is too small to be be easily detected. This report evaluates CI − transport across skins of higher PD (and lower conductance) in winter and further characterizes the system. Net CI − 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 be unique to these two species. It appears to be distinctly different from the acetazolamide-sensitive influx system seen in “low-CI −” solutions in skins of numerous species. The findings are discussed in terms of (1) parallel Na + and CI − active transport mechanisms and (2) a neutral NaCI-pump model, recently proposed by Rehm.