AJP - Regulatory, Integrative and Comparative Physiology, Vol 237, Issue 1 74-R79, Copyright © 1979 by American Physiological Society
Electrical and transport characteristics of skin of larval Rana catesbeiana
T. C. Cox and R. H. Alvarado
Carefully dissected, mounted, and bathed with Ringer solution, the larval
bullfrog skin has a resistance of about 9,000 omega.cm2 and a stable
transepithelial electrical potential of about 20 mV (inside +). A
short-circuit current of about 2 microA.cm-2 is generated that is
comparable in magnitude to the net inward flux of Na+. At open circuit the
flux ratio equation for Na+ is not satisfied. Larval skin is less sensitive
to ouabain, amiloride, and ADH than adult skin. The current-voltage (C-V)
relationship across the preparation is not linear; there are distinct
breaks in both the hyperpolarizing and hypopolarizing regions. The former
break, at about +130 mV, corresponds with a break observed in adult skin
that corresponds with ENa. The shunt resistance (RS) and active pathway
resistance (RA) were estimated by C-V curve analysis and by ion
substitution. The two methods yielded comparable values with RS about 11 k
omega.cm2 and RA about 62 k omega.cm2. It is suggested that transport is
limited by the number of entry sites for sodium at the apical border of
transport cells.
