DETERMINATION OF THE COUPLING RATIO OF THE Na-K PUMP RESPONSIBLE FOR TRANSEPITHELIAL Na TRANSPORT BY BLOCKADE OF K CHANNELS

Abstract

Publisher Summary This chapter focuses on the determination of the coupling ratio of the sodium–potassium pump responsible for transepithelial sodium (Na) transport by blockade of potassium (K) channels. It presents certain experiments that were performed on male and female frogs— Rana temporaria and Rana esculenta . The skins were mounted in Perspex chambers and bathed in stirred Ringer's solution. The gluconate Ringer's solution was hypotonic because the isotonic gluconate Ringer's solution caused a pronounced inhibition of the short circuit current (SCC). The 10 mM, 25 mM, and 50 mM KCl and K + gluconate Ringer's solution was produced by substituting Na + with K + . The short circuit experiments were performed according to the method by Ussing and Zerahn. Addition of Ba ++ to the IBS of the isolated frog skin resulted in an inhibition of the SCC and in an increase in the transepithelial resistance. Two to five minutes after the addition of Ba ++ , the SCC started to recover and the resistance started to decrease. The recovery phase was completed 20–90 min after the addition of Ba ++ . The recovery varied from 30% to 150%. Thus, in some cases, prolonged incubation with Ba ++ resulted in an activation of the SCC.