ISSN:
1432-2013
Keywords:
Frog skin
;
Junctional conductance
;
Voltagedivider ratio
;
Paracellular conductance
;
Membrane conductances
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract It has been suggested that distribution of lateral interspace resistance in association with a highly conductive junction can significantly affect the measurement of outer membrane(o)/epithelial(t) voltage divider ratios (F o=δV o/δV t), thereby leading to erroneous inferences regarding the outer membrane fractional resistance [fR o=R o/R c=R o/(R o+R i)], whereR o andR i are the outer and inner cell membrane resistance respectively andR c is the total cell membrane resistance. We present here experimental evidence for this point of view. During seasons when frog skins were highly permeable to Cl, transepithelial conductanceg t often exceeded 2 mS/cm2. High concentrations of external amiloride rapidly blocked cellular transport, butg t initially remained high andF o remained appreciably less than 1.0. These values ofF o were found here to result from low junctional resistanceR j: increase ofR j, either gradually following the administration of amiloride, or abruptly with external replacement of Cl by other anions, was associated with increase ofF o to near unity, without effect on the membrane potential or significant change in the short-circuit current. Experimental results following amiloride validated a simple equivalent circuit model predicting near-linear increase inF o with progressive decrease ing t and led to plausible values ofR j and lateral space resistanceR l. The possible influence of the paracellular resistance pattern on the evaluation of cell membrane resistances from voltage divider ratios is discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00652761
