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Coupling of volume and Na + transport in frog skin epithelium
Author(s) -
Tang CherngShing R.,
PetersonYantorno Kim,
Civan Mortimer M.
Publication year - 1989
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1111/j.1768-322x.1989.tb00833.x
Subject(s) - tonicity , biophysics , amiloride , apical membrane , frog skin , epithelial polarity , conductance , intracellular , biology , permeability (electromagnetism) , epithelium , sodium , osmole , anatomy , membrane potential , electrophysiology , water transport , stimulation , transepithelial potential difference , ion transporter , membrane , chemistry , biochemistry , endocrinology , water flow , mathematics , organic chemistry , combinatorics , neuroscience , environmental engineering , engineering , genetics
Whole skins and isolated epithelia were bathed with isotonic media (‐ 244 mOsm) containing sucrose or glucose. The serosal osmolality was intermittently reduced (to ‐ 137 mOsm) by removing the nonelectrolyte. Transepithelial and intracellular electrophysiological parameters were monitored while serosal osmolality was changed. Serosal hypotonicity increased the short‐circuit current (I sc ) and the basolateral conductance, hyperpolarized the apical membrane (Φ mc ), and increased the intracellular Na + concentration. The increases in apical conductance and apical Na + permeability (measured from Goldman fits of the relationship between amiloride‐sensitive current and Φ mc ) were not statistically significant. To verify that the osmotically induced changes in I sc were mediated primarily at the basolateral membrane, the basolateral membrane potential of the experimental area was clamped close to 0 mV by replacing the serosal Na + with K + in Cl − ‐free media. The adjoining control area was exposed to serosal Na + . Serosal hypotonicity produced a sustained stimulation of I sc across the control, but not across the adjoining depolarized tissue area. The current results support the concept that hypotonic cell swelling increases Na + transport across frog skin epithelium by increasing the basolateral K + permeability, hyperpolarizing the apical membrane, and increasing the electrical driving force for apical Na + entry.