Protein kinase A mediates activation of ATP-sensitive K+ currents by CGRP in gallbladder smooth muscle
Zhang, L.; Bonev, A.D.; Mawe, G.M.; Nelson, M.T.
American Journal of Physiology 267(3 Pt 1): G494-G499
1994
ISSN/ISBN: 0002-9513 PMID: 7943248 Document Number: 428332
The signal transduction mechanisms underlying the activation of ATP-sensitive potassium (KATP) current by calcitonin gene-related peptide (CGRP) in gallbladder smooth muscle were examined with intracellular microelectrode recording and whole cell patch-clamp techniques. In the intact gallbladder preparation, the adenylyl cyclase activator forskolin hyperpolarized the membrane potential and abolished spontaneous action potentials. This response was inhibited by the KATP channel blocker glibenclamide. CGRP (10 nM), forskolin (10 mM), the membrane-permeable adenosine 3',5'-cyclic monophosphate (cAMP) analogue adenosine 3',5'-cyclic monophosphothioate (Sp-cAMP[S]; 500 mM), and the catalytic subunit of protein kinase A (100 U/ml) activated glibendamide-sensitive currents in enzymatically dissociated gallbladder smooth muscle cells. CGRP activation of potassium currents was prevented by dialysis of the cell cytoplasm with guanosine 5'-O-(2-thiodiphosphate) (5 mM) or a specific peptide inhibitor of protein kinase A (2.3 mM). Okadaic acid (5 mM), phosphatase inhibitor, slowed the deactivation of the KATP current, following removal of CGRP. The results of this study indicate that CGRP hyperpolarizes gallbladder smooth muscle by elevation of cAMP and subsequent stimulation of protein kinase A. Reprinted by permission of the publisher.