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Stealth ryanodine‐sensitive Ca 2+ release contributes to activity of capacitative Ca 2+ entry and nitric oxide synthase in bovine endothelial cells
Author(s) -
PaltaufDoburzynska Jolanta,
Posch Karla,
Paltauf Guenther,
Graier Wolfgang F.
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.369bb.x
Subject(s) - ryanodine receptor , chemistry , extracellular , nitric oxide , nitric oxide synthase , thapsigargin , stimulation , calcium , fura 2 , medicine , intracellular , endocrinology , cytosol , biophysics , biochemistry , biology , enzyme , organic chemistry
1 The involvement of ryanodine‐sensitive Ca 2+ release (RsCR) in bradykinin (Bk)‐induced Ca 2+ release, capacitative Ca 2+ entry (CCE) and nitric oxide synthase (NOS) activation was assessed in freshly isolated bovine coronary artery endothelial cells. 2 Using deconvolution microscopy fura‐2 was found throughout the whole cytosol, while the cell membrane impermeable dye FFP‐18 was exclusively in the cell membrane. Thus, perinuclear ([Ca 2+ ] pn ) and subplasmalem m al Ca 2+ concentration ([Ca 2+ ] sp ) were monitored using fura‐2 and FFP‐18. 3 Inhibition of Na + −Ca 2+ exchange by lowering extracellular Na + concentration augmented the Bk‐induced [Ca 2+ ] pn signal in Ca 2+ ‐free solution. This effect was abolished when RsCR was prevented with 25 μm m u; m ol l −1 ryanodine, while inhibition of RsCR had no effect on Bk‐induced increase in [Ca 2+ ] pn without inhibition of Na + −Ca 2+ exchange. 4 Initiating RsCR by 200 n m ol l −1 ryanodine increased [Ca 2+ ] sp , while [Ca 2+ ] pn remained constant. However, when Na + −Ca 2+ exchange was prevented, ryanodine was also able to elevate [Ca 2+ ] pn . 5 Blockage of RsCR diminished Ca 2+ extrusion in response to stimulation with Bk in normal Na + ‐containing solution. 6 Inhibition of RsCR blunted Bk‐activated CCE, while inhibition of Na + −Ca 2+ exchange during stimulation enhanced CCE. 7 Although direct activation of RsCR failed to activate NOS, inhibition of RsCR diminished the effect of ATP and Bk on NOS, while the effect of thapsigargin remained unchanged. 8 These data suggest that during stimulation subplasmalem m al RsCR occurs, which contributes to the activities of CCE and NOS. Thus, the function of the subplasmalem m al Ca 2+ control unit must be extended as a regulator for CCE and NOS.