title: Modulation of murine gastric antrum smooth muscle STOC activity and excitability by phospholamban.
abstract: We investigated intracellular Ca(2+) waves, spontaneous transient outward currents (STOCs), and membrane potentials of gastric antrum smooth muscle cells from wild-type and phospholamban-knockout mice. The NO donor sodium nitroprusside (SNP) increased intracellular Ca(2+) wave activity in wild-type antrum smooth muscle cells, but had no effect on the constitutively elevated intracellular Ca(2+) wave activity of phospholamban-knockout cells. STOC activity was also constitutively elevated in phospholamban-knockout antrum smooth muscle cells relative to wild-type cells. SNP or 8-bromo-cGMP increased the STOC activity of wild-type antrum smooth muscle cells, but had no effect on STOC activity of phospholamban-knockout cells. Iberiotoxin, but not apamin, inhibited STOC activity in wild-type and phospholamban-knockout antrum smooth muscle cells. In the presence of SNP, STOC activity in wild-type and phospholamban-knockout antrum smooth muscle cells was inhibited by ryanodine, but not 2-APB. The cGMP-dependent protein kinase inhibitor KT5823 reversed the increase in STOC activity evoked by SNP in wild-type antrum smooth muscle cells, but had no effect on STOC activity in phospholamban-knockout cells. The resting membrane potential of phospholamban-knockout antrum smooth muscle cells was hyperpolarized by approximately -6 mV compared to wild-type cells. SNP hyperpolarized the resting membrane potential of wild-type antrum smooth muscle cells to a greater extent than phospholamban-knockout antrum smooth muscles. Despite the hyperpolarized membrane potential, slow wave activity was significantly increased in phospholamban-knockout antrum smooth muscles compared to wild-type smooth muscles. These results suggest that phospholamban is an important component of the mechanisms regulating the electrical properties of gastric antrum smooth muscles.
authors.affiliation: Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA.
authors.forename: Minkyung
authors.initials: M
authors.lastname: Kim
authors.forename: Grant W
authors.initials: GW
authors.lastname: Hennig
authors.forename: Kyungsik
authors.initials: K
authors.lastname: Park
authors.forename: In Soo
authors.initials: IS
authors.lastname: Han
authors.forename: Terence K
authors.initials: TK
authors.lastname: Smith
authors.forename: Sang Don
authors.initials: SD
authors.lastname: Koh
authors.forename: Brian A
authors.initials: BA
authors.lastname: Perrino