ISSN:
1432-2013
Schlagwort(e):
Ouabain
;
Frog kidney
;
Proximal tubule
;
Ion sensitive microelectrodes
;
Na+/K+ pump
;
Intracellular K+, Na+, Cl−, pH, Ca2+
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Medizin
Notizen:
Abstract Using conventional and ion selective microelectrodes, the effect of ouabain (10−4 mol/l) on peritubular cell membrane potential (PDpt), on intracellular pH (pHi) as well as on the intracellular ion activities of Cl− (Cl i − ), K+ (K i + ), Na+ (Na i + ) and Ca2+ (Ca i 2+ ) was studied in proximal tubules of the isolated perfused frog kidney. In the absence of ouabain (PDpt=−57.0±1.9 mV), the electrochemical potential difference of chloride (apparent {ie6-1} and of potassium {ie6-2} is directed from cell to bath, of H+ {ie6-3}, of Na+ {ie6-4} and of Ca2+ {ie6-5} from bath to cell. Ouabain leads to a gradual decline of PDpt, which is reduced to half (PDpt, 1/2) within 31±4.6 min (in presence of luminal glucose and phenylalanine), and to a decline of the absolute values of apparent {ie6-6}, of {ie6-7}, {ie6-8} and {ie6-9}. In contrast, an increase of {ei6-10} is observed. At PDpt, 1/2 apparent Cl i − increases by 6.2±1.0 mmol/l, pHi by 0.13±0.03, Ca i 2+ by 185±21 nmol/l, and Na i + by 34.2±4.6 mmol/l, whereas K i + decreases by 37.7±2.2 mmol/l. The results suggest that the application of ouabain is followed by a decrease of peritubular cell membrane permeability to K+, by an accumulation of Ca2+, Na+ and HCO 3 - in the cell and by a dissipation of the electrochemical Cl− gradient.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00581526
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