Heterogeneous gene expression and functional activity of ryanodine receptors in resistance and conduit pulmonary as well as mesenteric artery smooth muscle cells.
BACKGROUND
Hypoxia causes heterogeneous contractile responses in resistance and conduit pulmonary as well as systemic (mesenteric) artery smooth muscle cells (RPASMCs, CPASMCs and MASMCs), but the underlying mechanisms are largely unknown. In this study, we aimed to investigate whether the gene expression and functional activity of ryanodine receptors (RyRs) would be different in these 3 cell types.


METHODS
RyR mRNA expression, Ca(2+) sparks and [Ca(2+)](i) were measured by real-time quantitative RT-PCR, laser scanning confocal microscopy and wide-field fluorescence microscopy, respectively.


RESULTS
All 3 RyR subtype (RyR1, RyR2 and RyR3) mRNAs are expressed in RPASMCs, CPASMCs and MASMCs, but their expression levels are different. Spontaneous Ca(2+) sparks (functional events of RyRs) show distinct frequency, amplitude, duration, size and kinetics in these 3 cell types. Similarly, activation of RyRs by caffeine, 4-chloro-m-cresol or high K(+) induces differential Ca(2+) release. Moreover, hypoxia-induced increase in [Ca(2+)](i) is largest in MASMCs relative to CPSAMCs and smallest in RPASMCs.


CONCLUSIONS
This study provides comprehensive evidence that RyRs are heterogeneous in gene expression and functional activity in RPASMCs, CPASMCs and MASMCs, which may contribute to the diversity of excitation-contraction coupling and hypoxic Ca(2+) responses in different vascular smooth muscle cells.
Zheng
Yun-Min
YM
Center for Cardiovascular Sciences, Albany Medical College, Albany, NY 12158, USA.
Wang
Qing-Song
QS
Liu
Qing-Hua
QH
Rathore
Rakesh
R
Yadav
Vishal
V
Wang
Yong-Xiao
YX
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D015687:Cell Hypoxia; D003408:Cresols / Q000494:pharmacology; D005786:Gene Expression Regulation; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008638:Mesenteric Arteries / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D011651:Pulmonary Artery / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D003408:Cresols; D012333:RNA, Messenger; D019837:Ryanodine Receptor Calcium Release Channel; C006984:chlorocresol; D002110:Caffeine; D011188:Potassium