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Effect of insulin on area and Na+ channel density of apical membrane of cultured toad kidney cells.
Author(s) -
Erlij D,
De Smet P,
Van Driessche W
Publication year - 1994
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.1994.sp020461
Subject(s) - apical membrane , membrane potential , toad , biophysics , amiloride , paracellular transport , chemistry , membrane , epithelial polarity , endocrinology , medicine , stimulation , biology , sodium , biochemistry , permeability (electromagnetism) , organic chemistry
1. The stimulation of transepithelial Na+ transport caused by insulin in A6 cultured toad kidney cells was investigated by determination of membrane capacitance (Cm), short circuit current (Isc) and current fluctuation analysis. Values of Cm are proportional to membrane area while blocker‐induced current fluctuation analysis provides an estimate of the number of active amiloride‐sensitive Na+ channels in the apical membrane. 2. Insulin simultaneously increased Cm, Isc and Gt (transepithelial conductance) in epithelia incubated with Na(+)‐containing solutions on both sides. 3. Analysis of 6‐chloro‐3,5‐diaminopyrazine‐2‐carboxamide (CDPC)‐induced noise showed that insulin increased the number of active Na+ channels in the apical membrane, without altering the single channel current. 4. When nystatin was used to permeabilize the apical membrane the impedance data revealed the presence of a second time constant. Analysis of these data indicated that the basolateral membrane capacitance (Cb) is much larger than the apical membrane capacitance (Ca). Insulin administered to nystatin‐treated epithelia increased the values for both capacitances. 5. We suggest that the stimulation of transepithelial Na+ transport caused by insulin may be associated with the exocytotic delivery of transporters to the apical membrane.