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Attenuated PLC‐Dependent Activation of Voltage‐Gated Ca 2+ Entry in Pulmonary Endothelium Following Chronic Hypoxia
Author(s) -
Paffett Michael L.,
Resta Thomas C.,
Kanagy Nancy L.,
Walker Benjimen R.
Publication year - 2008
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.22.1_supplement.1209.9
Subject(s) - purinergic receptor , phospholipase c , pulmonary hypertension , chemistry , stimulation , protein kinase c , endocrinology , receptor , hypoxia (environmental) , pharmacology , medicine , signal transduction , biochemistry , oxygen , organic chemistry
Chronic hypoxia (CH)‐induced pulmonary hypertension is associated with reduced endothelial cell (EC) receptor‐operated Ca 2+ (ROC) entry. Voltage‐gated Ca 2+ channels (VGCC) are present in pulmonary ECs and are activated by protein kinase C (PKC). Although VGCCs may participate in ROC entry, neither the role of phospolipase C (PLC) nor the effect of CH on this entry pathway are known. We hypothesized that CH reduces phospholipase C (PLC)‐induced Ca 2+ influx through VGCCs in pulmonary ECs. Thus, we assessed both KCl and ATP‐induced Ca 2+ entry in freshly isolated, fura‐2 loaded ECs obtained from control and CH rats (4 wk at 0.5 atm). Consistent with earlier findings, KCl‐induced Ca 2+ entry was diminished following CH. Furthermore, KCl‐mediated Ca 2+ influx in control ECs was attenuated by the T‐type VGCC inhibitor, mibrefradil (MBF; 10 μM), but not by the L‐type inhibitor diltiazem (50 μM). Similarly, ATP‐induced Ca 2+ entry in control ECs was reduced to the level of CH ECs by MBF and was partially inhibited by the ROC blocker SKF96365 (20 μM). Neither of these antagonists affected Ca 2+ entry in CH ECs. Finally, the PLC inhibitor U73122 (1 μM) abolished ATP‐induced Ca 2+ influx in ECs from both control and CH rats, but the inactive analog U73343 was without effect. These data suggest that purinergic receptor stimulation in pulmonary ECs activates T‐type VGCCs through a PLC‐dependent mechanism that is diminished following CH.