Comparative Capacitative Calcium Entry Mechanisms in Canine Pulmonary and Renal Arterial Smooth Muscle Cells

Abstract

Experiments were performed to determine whether capacitative Ca(2+) entry (CCE) can be activated in canine pulmonary and renal arterial smooth muscle cells (ASMCs) and whether activation of CCE parallels the different functional structure of the sarcoplasmic reticulum (SR) in these two cell types. The cytosolic [Ca(2+)] was measured by imaging fura-2-loaded individual cells. Increases in the cytosolic [Ca(2+)] due to store depletion in pulmonary ASMCs required simultaneous depletion of both the inositol 1,4,5-trisphosphate (InsP(3))- and ryanodine (RY)-sensitive SR Ca(2+) stores. In contrast, the cytosolic [Ca(2+)] rises in renal ASMCs occurred when the SR stores were depleted through either the InsP(3) or RY pathways. The increase in the cytosolic [Ca(2+)] due to store depletion in both pulmonary and renal ASMCs was present in cells that were voltage clamped and was abolished when cells were perfused with a Ca(2+)-free bathing solution. Rapid quenching of the fura-2 signal by 100 microM Mn(2+) following SR store depletion indicated that extracellular Ca(2+) entry increased in both cell types and also verified that activation of CCE in pulmonary ASMCs required the simultaneous depletion of the InsP(3)- and RY-sensitive SR Ca(2+) stores, while CCE could be activated in renal ASMCs by the depletion of either of the InsP(3)- or RY-sensitive SR stores. Store depletion Ca(2+) entry in both pulmonary and renal ASMCs was strongly inhibited by Ni(2+) (0.1-10 mM), slightly inhibited by Cd(2+) (200-500 microM), but was not significantly affected by the voltage-gated Ca(2+) channel (VGCC) blocker nisoldipine (10 microM). The non-selective cation channel blocker Gd(3+) (100 microM) inhibited a portion of the Ca(2+) entry in 6 of 18 renal but not pulmonary ASMCs. These results provide evidence that SR Ca(2+) store depletion activates CCE in parallel with the organization of intracellular Ca(2+) stores in canine pulmonary and renal ASMCs.

Impaired NO-dependent inhibition of store- and receptor-operated calcium entry in pulmonary vascular smooth muscle after chronic hypoxia

“…The changes in [Ca 2ϩ ]i (SOCE) and ID were then determined upon restoration of extracellular Ca 2ϩ (1.8 mM) in the continued presence of diltiazem and CPA or TG. Separate sets of arteries from each group were pretreated with the relatively nonselective inhibitor of Ca 2ϩ entry, NiCl2 (10 mM) (40). Parallel experiments were performed in the presence of SKF-96365 (50 M), which has been reported to selectively inhibit ROCE vs. SOCE (8,12,25).…”

Regulation of calcium signaling by polycystin-2

“…7, 100, 101, and 151). One of the most prevalent pathways implicated in the Ca 2ϩ rise in nonexcitable cells is the triggering of PLC activation and the subsequent production of the ligands DAG and IP 3 (7,38,74,75,100,101,138) (Fig. 5).…”

Long-Term Maternal Hypoxia

“…16,44 This is important as removal of extracellular Ca 2þ can reduce the Ca 2þ concentration in the sarcoplasmic reticulum and thereby limit the Ca 2þ responses due to 5-HT. Extracellular Ca 2þ entry was selectively reduced by treating arteries with 10 mmol/L Ni 2þ because at a high concentration, Ni 2þ blocks plasma membrane Ca 2þ entry without inhibiting intracellular Ca 2þ release.…”