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The sodium‐transporting compartment of the epithelium of frog skin
Author(s) -
Cereijido M.,
Rabito C. A.,
Boulan E. Rodríguez,
Rotunno Catalina A.
Publication year - 1974
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1974.sp010498
Subject(s) - frog skin , compartment (ship) , chemistry , sodium , biophysics , amiloride , function (biology) , mole , anatomy , analytical chemistry (journal) , chromatography , biology , biochemistry , geology , oceanography , organic chemistry , evolutionary biology
1. The abdominal frog skin was mounted between two chambers containing Ringer with 1 m M ‐Na on the outside and 115 m M ‐Na on the inside. When the Na concentration of the outer solution ([Na] o ) is instantaneously raised from 1 to 50 m M , the short circuit current ( I ) increases to a new value in less than a second, and becomes essentially time‐independent. Only in a few experiments was it observed to increase further, although at a much slower rate. 2. At a time t after this increase, the addition of 10 −4 M amiloride to the outer solution produces an exponential decrease of I . The area under this exponential curve is generally taken to reflect the existence of a Na‐ transporting compartment (NaTC). 3. The amount of Na represented by NaTC is a function of t : it increases from 1·7 × 10 −9 mole. cm −2 , at t = 10 sec, to 22·8 × 10 −9 mole. cm −2 at t = 10 min. 4. In view of the fact that ( a ) I is not a function of the size of the ‘NaTC’ and ( b ) that whereas I reaches a steady value in a fraction of a second the size of NaTC keeps increasing for minutes, it is proposed that the ‘NaTC’ represents an amount of Na which is not located along the main route of transepithelial transport. 5. On the assumption that the NaTC is located in a cellular compartment and that, in order to accumulate in this compartment Na should be accompanied by a permeable anion, a series of experiments were performed with Ringer in which Cl − was replaced by gluconate. It was observed as expected, that NaTC in gluconate is 164 times smaller than in Cl − , but I only decreases to one half its value in Cl − Ringer.