Electrical and transport characteristics of skin of larval Rana catesbeiana
Cox, T.C.; Alvarado, R.H.
American Journal of Physiology 237(1): R74-R79
1979
ISSN/ISBN: 0002-9513 PMID: 313715 Document Number: 140719
Carefully dissected, mounted and bathed with Ringer solution, the larval bullfrog skin has a resistance of .apprx. 9000 .OMEGA. .cntdot. cm2 and a stable transepithelial electrical potential of .apprx. 20 mV (inside +). A short-circuit current of about 2 .mu.A .cntdot. 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 2 methods yielded comparable values with Rs about 11 k.OMEGA. .cntdot. cm2 and RA about 62 .OMEGA. .cntdot. cm2. Transport is evidently limited by the number of entry sites for Na at the apical border of transport cells.