TY - JOUR

T1 - Estimation of intracellular Na activity and of Na permeability from current voltage curves of Na channels in frog skin

AU - Fuchs, W.

AU - Larsen, E. H.

AU - Lindemann, B.

PY - 1975

Y1 - 1975

N2 - Na specific passive transport channels in the apical membrane of the str. granulosum control the input step of Na transport through frog skin epithelium. Their permeability decreases with acidification of the outer bathing medium (apparent pK = 4.1, complete closure of channels at pH 3). Phosphate or COO groups of the membrane can be responsible for this behaviour. To characterize the group the carbodiimide glycine methylester method was used (Hoare and Koshland, 1967). The inward facing membranes of abdominal skins of r. temporaria and r. esculenta were depolarized with high K concentrations, such that the apical membrane determined the electrical properties of the skin. After some control recordings the outer surface was exposed for 10 min to a Na free solution containing 25 mM Carbodiimide, 75 mM glycine methylester 1 mM CaCl2 and 5 mM TRIS, pH 3.5, then washed with Ringer's. Membrane resistance (increased) and short circuit current (decreased to zero) were now independent of pH (between 3 and 7) and outer Na concentration, just as during complete blockage of Na current by amiloride. The carbodiimide glycine methylester blockage is irreversible and acid stable (which excludes phosphate groups). Apparently the Na channels (or their immediate vicinity) contain COO groups. The channels are blocked when these groups are protonated or modified with nucleophilic reagents.

AB - Na specific passive transport channels in the apical membrane of the str. granulosum control the input step of Na transport through frog skin epithelium. Their permeability decreases with acidification of the outer bathing medium (apparent pK = 4.1, complete closure of channels at pH 3). Phosphate or COO groups of the membrane can be responsible for this behaviour. To characterize the group the carbodiimide glycine methylester method was used (Hoare and Koshland, 1967). The inward facing membranes of abdominal skins of r. temporaria and r. esculenta were depolarized with high K concentrations, such that the apical membrane determined the electrical properties of the skin. After some control recordings the outer surface was exposed for 10 min to a Na free solution containing 25 mM Carbodiimide, 75 mM glycine methylester 1 mM CaCl2 and 5 mM TRIS, pH 3.5, then washed with Ringer's. Membrane resistance (increased) and short circuit current (decreased to zero) were now independent of pH (between 3 and 7) and outer Na concentration, just as during complete blockage of Na current by amiloride. The carbodiimide glycine methylester blockage is irreversible and acid stable (which excludes phosphate groups). Apparently the Na channels (or their immediate vicinity) contain COO groups. The channels are blocked when these groups are protonated or modified with nucleophilic reagents.

UR - http://www.scopus.com/inward/record.url?scp=0345892934&partnerID=8YFLogxK

M3 - Journal article

AN - SCOPUS:0345892934

VL - 355

SP - No. 141

JO - Pflügers Archiv - European Journal of Physiology

JF - Pflügers Archiv - European Journal of Physiology

SN - 0031-6768

IS - Sup.

ER -