Localized Ca2+ uncaging induces Ca2+ release through IP3R in smooth muscle.
OBJECTIVE
Our previous study indicated that there are two types of Ca2+ release events seen in intact mouse bladder tissue. In this study our aim is to investigate the mechanism that underlies the phenomena of Ca2+ release in smooth muscle.


METHODS
Single cells were isolated and tissue segments were prepared by cutting the detrusor into 0.1 cm x 0.5 cm strips running along the axis from the neck to the fundus. Single cells and intact tissue strips were co-loaded with the Ca2+ indicator and caged Ca2+ by incubation with 10 micromol/L Fluo-4 AM and DMNP-EDTA-AM. Fluo-4 AM fluorescence was detected by laser scanning confocal microscopy, and local uncaging of DMNP-EGTA was achieved by brief exposure to the output of a diode-pumped, Ti:sapphire laser tuned to 730 nm.


RESULTS
Local uncaging of caged Ca2+ was able to trigger Ca2+ release events in both single cells and tissue strips from mouse bladder. The Ca2+ release events could not be blocked by ryanodine alone, but the property of the Ca2+ release was markedly altered. Surprisingly, in the presence of ryanodine, Xestospongin C completely inhibited the Ca2+ release events both in single cell and tissue experiments.


CONCLUSIONS
(1) Two photon flash photolysis (TPFP) triggers Ca2+ induced Ca2+ release. This process involves release through type 2 ryanodine receptor channels; (2) TPFP results in the release of Ca2+ through inositol 1,4,5-trisphosphate receptors in the absence of phospholipase C activation.
Wang
Min
M
Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Chen
Zheng
Z
Xing
Yan
Y
Zhang
Xu
X
Dong
Xian-zhi
XZ
Ji
Guang-ju
GJ
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D047028:Macrocyclic Compounds / Q000494:pharmacology; D051379:Mice; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D010080:Oxazoles / Q000494:pharmacology; D010782:Photolysis; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D014466:Ultraviolet Rays; D001743:Urinary Bladder / Q000378:metabolism*
D053496:Inositol 1,4,5-Trisphosphate Receptors; D047028:Macrocyclic Compounds; D010080:Oxazoles; D019837:Ryanodine Receptor Calcium Release Channel; C511704:xestospongin C; D012433:Ryanodine; D002118:Calcium