AJP - Regulatory, Integrative and Comparative Physiology, Vol 244, Issue 1 58-R65, Copyright © 1983 by American Physiological Society
Nystatin studies of the skin of larval Rana catesbeiana
T. C. Cox and R. H. Alvarado
Transport and electrical characteristics of the isolated skin of larval
Rana catesbeiana were analyzed using ion substitution and nystatin. When
the inner (IBS) and outer (OBS) bathing solutions contained Na Ringer
solution the electrical potential (TEP), short-circuit current (SCC), and
resistance (R2) were 23.5 +/- 7.0 mV, 2.8 +/- 0.7 microA . cm-2, and 8.00
+/- 0.74 k omega. cm2, respectively (n = 4). When K was substituted for Na
in the OBS these values were not changed significantly. When nystatin (120
U.cm-3), a drug that increases the permeability of membranes to small
cations, was added to the OBS (Na Ringer) there was a striking increase in
the TEP to 52.8 +/- 3.1 mV, SCC to 14.8 +/- 2.0 microA . cm-2, and drop in
R2 to 3.75 +/- 0.52 k omega . cm2. The response to nystatin was similar
with Na or K Ringer solution in the OBS (Na Ringer in the IBS). With Na
Ringer in the OBS and IBS, the increase in SCC induced by low doses of
nystatin equaled net Na flux measured isotopically. Plots of
transepithelial conductance against SCC after nystatin were linear and
provided estimates of shunt resistance (R*sh = 14.6 +/- 1.3 k omega . cm2)
and electromotive driving force for ions (E*A = 76 +/- 3 mV). Similar
curves were obtained with K Ringer in the OBS. In the presence of nystatin,
characteristics of the basolateral membrane were evaluated. It displayed
selective permeability to K relative to Na or Tris.
