The effect of furosemide on potential difference (PD) and on short-circuit current (SCC) was analysed in isolated skin of Rana esculenta. Furosemide was either administered from the epithelial side, from the corial side, or from both sides of the skin in chloride-or sulfate-Ringer solution. The interaction of furosemide with inhibitors of known site of action, amiloride and ouabain, was investigated.
| 1. |
Furosemide increases immediately SCC and PD when the epithelial side of the skin is exposed. Resistance is reduced.
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| 2. |
Furosemide lowers SCC and PD with a delay when the corial side of the skin is exposed.
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In short-circuited skins furosemide stimulates SCC from the epithelial side, too, and decreases it from the corial side.
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Addition of furosemide to both sides of the skin results in an immediate increase of PD and SCC followed by a spontaneous decrease.
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The effect of furosemide from the epithelial side is not different in chloride-or sulfate-Ringer. SCC is more enhanced than PD.
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Furosemide exerts the same relative effects on PD and SCC in amiloride treated skins and in control skins when both drugs are applied from the epithelial side.
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The relative inhibition of PD and SCC by amiloride is the same in control and furosemide stimulated skins.
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| 8. |
The decrease of PD and SCC induced by ouabain applied from the corial side can not be influenced by addition of furosemide to the epithelial bath.
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| 9. |
Ouabain reduces PD and SCC concentration dependent to the same absolute value in control skins and in skins which are stimulated by furosemide in the epithelial bath.
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| 10. |
The hypothesis is discussed that furosemide increases the entrance of sodium into the transport compartment of the active cell layer from that side from which it reaches this cell layer. This results either in an increased net transfer (epithelial side) or in a decreased efficiency of the unimpaired pump with diminished net transfer (corial side).
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Key words Frog Skin - Sodium Transport - Permeability - Furosemide - Amiloride - Ouabain
Preliminary reports of the results were presented in part at the spring meetings of the Deutsche Pharmakologische Gesellschaft 1971 and 1973.