title: Atrial natriuretic peptide and cGMP activate sodium transport through PKA-dependent pathway in the urinary bladder of the Japanese tree frog.
abstract: The effects of atrial natriuretic peptide (ANP) and cGMP on transepithelial ion transport were examined in the urinary bladder of the Japanese tree frog, Hyla japonica, using Ussing chamber voltage-clamp and whole-cell patch-clamp techniques. When the bladders were exposed to 4.4 x 10(-11) to 10(-6) M ANP or 10(-7) to 3 x 10(-4) M 8-Br-cGMP, both the transepithelial potential difference (PD) and the short-circuit current (Isc) were significantly increased in a concentration-response manner. The cGMP-dependent responses were inhibited in a Na+-free bath solution and in the presence of amiloride. The cGMP-dependent increases in Isc were significantly inhibited by specific PKA inhibitors (5 x 10(-7) M KT-5720 and >10(-5) M H-89), but not by a specific PKG inhibitor (5 x 10(-7) M KT-5823). ANP-dependent increases in Isc were also significantly inhibited by KT-5720. In the patch-clamp study, ANP and cGMP significantly increased in inward currents involving Na+ uptake. These results suggest that a cross-talk mechanism exists between cAMP and cGMP signaling pathways, which leads to Na+ transport in the frog urinary bladder. In addition, the cGMP-dependent increases in Isc were partially inhibited by 10(-4) M l-cis-diltiazem, a specific inhibitor of cyclic nucleotide-gated (CNG) channels. These results also suggest a relation between CNG channels and the cGMP-dependent increases in Na+ absorption of the frog urinary bladder.
authors.affiliation: Department of Life and Environmental Science, Graduate school of Science and Engineering, 3190 Gofuku, Toyama 930-8555, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Yamada
authors.forename: Kouhei
authors.initials: K
authors.lastname: Matsuda
authors.forename: Minoru
authors.initials: M
authors.lastname: Uchiyama
mesh_terms: D000818:Animals; D001001:Anura / Q000502:physiology* / Q000652:urine; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D001693:Biological Transport, Active; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism*; D004594:Electrophysiology; D012964:Sodium / Q000378:metabolism*; D001743:Urinary Bladder / Q000166:cytology / Q000502:physiology*
chemical_list: D009320:Atrial Natriuretic Factor; D012964:Sodium; D017868:Cyclic AMP-Dependent Protein Kinases; D006152:Cyclic GMP