Transport Processes, Metabolism and Endocrinology; Kidney, Gastrointestinal Tract, and Exocrine Glands

Pflügers Archiv

, Volume 394, Issue 2, pp 130-138

First online:

Kinetic studies on the effects of ouabain on Na+ fluxes in frog skin

  • Ernst G. HufAffiliated withDepartments of Medicine and Pharmacy and Pharmaceutics, Medical College of Virginia, Virginia Commonwealth University
  • , John R. HowellAffiliated withDepartments of Medicine and Pharmacy and Pharmaceutics, Medical College of Virginia, Virginia Commonwealth University
  • , Peter A. BoswellAffiliated withDepartments of Medicine and Pharmacy and Pharmaceutics, Medical College of Virginia, Virginia Commonwealth University

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Abstract

Among 48 pieces of paired frog skins ofRana pipiens in Ringer's solution, 10 pieces showed a strictly monotone decrease in the short circuit current (SCC) following ouabain treatment (10−4 M). In 9 cases a transient attenuation, and in 27 cases a distinct wave in the ebb of the SCC, was seen. In 2 instances, two waves were seen. Associated with the not-monotone events was a transient rise in electrical skin conductance. The reasons for these mixed skin responses are unknown. One possible reason is considered here: Early during the ouabain action, some of the Na+ entering from the mucosal side is trapped in the skin by electroneutral processes, in keeping with the already known fact that ultimately cellular KCl is partly replaced by NaCl. Computer assisted model studies show how monotone, and not-monotone “transepithelial” net Na+ flux curves can be generated. Essential conditions for the generation of notmonotone Na+ flux curves are: 1. Presence of two distinct “cellular”, active Na+ pools in the model. 2. Presence of a loop pathway in which a principal “transepithelial Na+ transport compartment”, and a constitutent “Na+/K+ maintenance compartment”, are connected to each other and to the “extracellular” compartment. The model, then, predicts under which kinetic conditions monotone and not-monotone transepithelial Na+ flux curves will be seen.

Key words

Frog skin Ouabain Short-circuit current Na+ transport Na+ pools Computer simulation