ISSN:
1432-1424
Schlagwort(e):
Frog skin
;
microelectrodes
;
membrane potentials
;
intracellular activities
;
amiloride
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Chemie und Pharmazie
Notizen:
Summary Intracellular Na+, K+, and Cl− activities (a Na i ,a K i ,a Cl i ) and transapical membrane potentials (V o) were measured with liquid ion-exchanger and open-tip microelectrodes in isolated short-circuited frog skins (R. pipiens) incubated at 23°C in normal amphibian Ringer's solution. Under control conditionsa Na i =14±3mm,a K i =132±10mm anda Cl i =18±3mm (sd). The value ofa Cl i is 4.4 times the value corresponding to electrochemical equilibrium for this ion. Thus, Cl− is actively accumulated by epithelial cells of the frog skin. Shortly after addition of amiloride (2–5 μm) to the apical bathing medium,a K i ,a Na i , anda Cl i were essentially unchanged althoughV o had hyperpolarized by about 30–40 mV. During long-term exposure to amiloridea K i anda Cl i did not change significantly,V o depolarized by about 16 mV from the maximal value anda Na i decreased to 8±3mm. Immediately after exposure to amiloride the transmembrane driving force for Na+ increased from 124 to 154 mV. During further exposure to amiloride, despite changes in bothV o anda Na i , this driving force remained virtually constant. SinceI sc during this period was close to zero, it is suggested that the observed driving force for Na+ under these conditions approximates the maximal driving force generated by the Na+−K+ ATP-ase pump in the basolateral cell membrane.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF02007639
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