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- Title
Frog atrial natriuretic peptide and cGMP activate amiloride-sensitive Na<sup>+</sup> channels in urinary bladder cells of Japanese tree frog, Hyla japonica.
- Authors
Yamada, Toshiki; Konno, Norifumi; Matsuda, Kouhei; Uchiyama, Minoru
- Abstract
In our previous study, it was suggested that ANP and cGMP may increase Na+ absorption in the urinary bladder of the Japanese tree frog, Hyla japonica. Thus, Na+ transport activated by ANP was investigated electrophysiologically by using a cell-attached patch-clamp technique in freshly isolated cells from the urinary bladder. A predominant channel expressed was a low conductance Na+ channel in the epithelial cells. The channel exhibited conductance for inward currents of 4.9 ± 0.2 pS, long open and closed times (c.a. 190 ms), and positive reversal potential. The channel activity was decreased under the pipette solution including 10−6 M amiloride. These characteristics were similar to those of amiloride-sensitive Na+ channels (ENaC). Addition of 10−9 M ANP activated and significantly increased the ENaC activity from 0.58 ± 0.09 to 1.47 ± 0.34. On the other hand, mean amplitudes and conductance of single channel did not change significantly after the addition of ANP. Addition of 10−5 M 8-Br-cGMP also activated the ENaC and significantly increased the channel activity from 0.56 ± 0.10 to 2.00 ± 0.33. The addition of ANP failed to activate the ENaC in the presence of 10−6 M amiloride. These results suggested that ANP and cGMP activate Na+ transport via ENaC in the epithelial cells of frog urinary bladder.
- Subjects
BLADDER; FROG anatomy; HYLIDAE; ATRIAL natriuretic peptides; AMILORIDE; PHYSIOLOGY
- Publication
Journal of Comparative Physiology B: Biochemical, Systemic & Environmental Physiology, 2007, Vol 177, Issue 5, p503
- ISSN
0174-1578
- Publication type
Article
- DOI
10.1007/s00360-007-0148-5