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Depolarization Evokes Calcium Entry Through Ca V 3.1 Channels in Lung Microvascular Endothelium in situ .
Author(s) -
Kuebler Wolfgang M.,
Chen Hairu,
Yin Jun,
Zhou Chun,
Wu Songwei
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a749-b
Subject(s) - depolarization , biophysics , voltage dependent calcium channel , chemistry , membrane potential , patch clamp , endothelium , channel blocker , calcium , electrophysiology , biology , medicine , endocrinology , biochemistry , receptor , organic chemistry
Pulmonary microvascular endothelial cells (PMVECs) express a voltage‐gated T‐type Ca 2+ channel Ca V 3.1 subunit that has been proposed to contribute to agonist‐induced Ca 2+ entry. Ca 2+ entry via Ca V 3.1 channel occurs when PMVEC membrane potential is within the CaV3.1 “window current” range of voltages that is predicted to be −60 to −30 mV. In the present study, we performed experiments to directly detect Ca 2+ influx within the window current range of voltages. Utilizing whole‐cell patch‐clamp recordings, cultured PMVECs were depolarized at potentials of −45 mV and 0 mV for 1.5 s, and then the inward Ca 2+ current was evaluated by measuring the deactivation tail current by transitioning to −120 mV. The tail current measurement revealed a PMVEC Ca 2+ conductance in the T‐type window current range of voltages. We further performed in situ subpleural microvascular fluorescence microscopy in isolated perfused rat lungs to examine whether infusion of KCl at high concentration (40 mM) results in an elevation of cytosolic Ca 2+ ([Ca 2+ ] i ) in lung microvascular endothelium. KCl reproducibly induced a slowly developing, sustained increase in [Ca 2+ ] i from 101±2 nM to 138±4 nM in microvascular endothelium ( P <0.05), an effect that was completely inhibited by the T‐type Ca 2+ channel blocker mibefradil (10 μM; n =5 each, P <0.05). Together, these results suggest that Ca V 3.1 T‐type Ca2+ channel is expressed in pulmonary microvascular endothelial cells and mediates depolarization‐induced [Ca 2+ ] i transitions both in culture and in situ . Supported by HL074116 and Kaiserin‐Friedrich Foundation