AJP - Cell Physiology, Vol 256, Issue 6 C1145-C1152, Copyright © 1989 by American Physiological Society
8-BrcAMP-induced capacitance and transport of H2O and Na in skin and urinary bladder of urodele amphibians
R. B. Silver and L. G. Palmer
Department of Physiology, Cornell University Medical College, New York, New York 10021.
The effects of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) on
capacitance (C), osmotic water flow (Jv), and amiloride-sensitive
short-circuit current (INa) were studied in bladder and skin derived from
the tiger salamander (aquatic and postmetamorphosed terrestrial phase).
8-BrcAMP-dependent increases in C, measured from the transepithelial
voltage response to constant current pulses, occurred in aquatic (delta C =
44%) and terrestrial (delta C = 61%) bladders and terrestrial skin (delta C
= 19%). Jv (200-mosM gradient, mucosal side hypotonic) was observed in the
bladders and was further enhanced by addition of 8-BrcAMP [10(-3) M; delta
Jv = 0.42 microliter.min-1.microF-1 (aquatic) and 0.32
microliter.min-1.microF-1 (terrestrial)]. The aquatic and terrestrial skins
were relatively impermeable to water, but the terrestrial skin showed a
small response to 8-BrcAMP (delta Jv = 0.04 microliter.min-1.microF-1).
8-BrcAMP-mediated natriferic responses were observed in aquatic bladder
(delta INa = 62%) and terrestrial skin (delta INa = 105%). Antidiuretic
hormone (ADH)-induced Jv was also observed in the aquatic bladder (delta Jv
= 0.33 microliter.min-1.microF-1) and was similar to the 8-BrcAMP-mediated
Jv measured in this tissue. The terrestrial bladder displayed a more
vigorous response to 8-BrcAMP than to ADH (delta JvADH = 0.09
microliter.min-1.microF-1 and delta Jv8-BrcAMP = 0.32
microliter.min-1.microF-1), suggesting that diminished sensitivity to ADH
accompanies the transition from water to land in this species.
