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Ca2+-pumps and Na2+-Ca2+-exchangers in coronary artery endothelium versus smooth muscle.

Szewczyk MM, Davis KA, Samson SE, Simpson F, Rangachari PK, Grover AK - J. Cell. Mol. Med. (2007 Jan-Feb)

Bottom Line: Vascular endothelial cells (EC) and smooth muscle cells (SMC) require a decrease in cytoplasmic Ca2+ concentration after activation.Since the two cell types differ in their structure and function, we compared the activities of PMCA, NCX and SERCA in pig coronary artery EC and SMC, the types of isoforms expressed using RT-PCR, and their protein abundance using Western blots.PMCA, SERCA and NCX differ in their affinities for Ca2+ and regulation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada.

ABSTRACT
Vascular endothelial cells (EC) and smooth muscle cells (SMC) require a decrease in cytoplasmic Ca2+ concentration after activation. This can be achieved by Ca2+ sequestration by the sarco-/endoplasmic reticulum Ca2+ pumps (SERCA) and Ca2+ extrusion by plasma membrane Ca2+ pumps (PMCA) and Na+-Ca2+-exchangers (NCX). Since the two cell types differ in their structure and function, we compared the activities of PMCA, NCX and SERCA in pig coronary artery EC and SMC, the types of isoforms expressed using RT-PCR, and their protein abundance using Western blots. The activity of NCX is higher in EC than in SMC but those of PMCA and SERCA is lower. Consistently, the protein abundance for NCX protein is higher in EC than in SMC and those of PMCA and SERCA is lower. Based on RT-PCR experiments, the types of RNA present are as follows: EC for PMCA1 while SMC for PMCA4 and PMCA1; EC for SERCA2 and SERCA3 and SMC for SERCA2. Both EC and SMC express NCX1 (mainly NCX1.3). PMCA, SERCA and NCX differ in their affinities for Ca2+ and regulation. Based on these observations and the literature, we conclude that the tightly regulated Ca2+ removal systems in SMC are consistent with the cyclical control of contractility of the filaments and those in EC are consistent with Ca2+ regulation of the endothelial nitric oxide synthase near the cell surface. The differences between EC and SMC should be considered in therapeutic interventions of cardiovascular diseases.

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Time course of NCX activity in EC and SMC. A. 45Ca2+ uptake by Na+-loaded EC or SMC from Na+-free and Na+-containing solutions. B. NCX-dependent 45Ca2+ uptake in EC and SMC defined as difference between the uptake in Na+-free and Na+-containing solutions in A.
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fig05: Time course of NCX activity in EC and SMC. A. 45Ca2+ uptake by Na+-loaded EC or SMC from Na+-free and Na+-containing solutions. B. NCX-dependent 45Ca2+ uptake in EC and SMC defined as difference between the uptake in Na+-free and Na+-containing solutions in A.

Mentions: NCX activity was determined as 45Ca2+ entry into Na+-loaded cells in Na+-free solutions. Na+-loaded cells (EC or SMC) were placed in normal Na+ or in Na+ substituted with N-methylglucamine (Fig. 5A), and the difference in the 45Ca2+ entry between them was defined as NCX activity (Fig. 5B). Time course of the uptake in Figure 5B shows that the NCX-dependent 45Ca2+ accumulation was linear for 5 min and that the rate of this accumulation was significantly greater in EC than in SMC. This uptake was inhibited by KB-R 7943 and monensin. When examined in several experiments, the NCX activity in EC (0.89 ±0.09 nmol/min/mg protein) was greater than in SMC (0.2 ± 0.01 nmol/min/mg protein). The NCX activity in EC was 447 ± 43% of that in SMC. The greater activity of NCX in EC than in SMC is consistent with the greater NCX1 protein abundance observed in Western blots in Fig. 4.


Ca2+-pumps and Na2+-Ca2+-exchangers in coronary artery endothelium versus smooth muscle.

Szewczyk MM, Davis KA, Samson SE, Simpson F, Rangachari PK, Grover AK - J. Cell. Mol. Med. (2007 Jan-Feb)

Time course of NCX activity in EC and SMC. A. 45Ca2+ uptake by Na+-loaded EC or SMC from Na+-free and Na+-containing solutions. B. NCX-dependent 45Ca2+ uptake in EC and SMC defined as difference between the uptake in Na+-free and Na+-containing solutions in A.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4401226&req=5

fig05: Time course of NCX activity in EC and SMC. A. 45Ca2+ uptake by Na+-loaded EC or SMC from Na+-free and Na+-containing solutions. B. NCX-dependent 45Ca2+ uptake in EC and SMC defined as difference between the uptake in Na+-free and Na+-containing solutions in A.
Mentions: NCX activity was determined as 45Ca2+ entry into Na+-loaded cells in Na+-free solutions. Na+-loaded cells (EC or SMC) were placed in normal Na+ or in Na+ substituted with N-methylglucamine (Fig. 5A), and the difference in the 45Ca2+ entry between them was defined as NCX activity (Fig. 5B). Time course of the uptake in Figure 5B shows that the NCX-dependent 45Ca2+ accumulation was linear for 5 min and that the rate of this accumulation was significantly greater in EC than in SMC. This uptake was inhibited by KB-R 7943 and monensin. When examined in several experiments, the NCX activity in EC (0.89 ±0.09 nmol/min/mg protein) was greater than in SMC (0.2 ± 0.01 nmol/min/mg protein). The NCX activity in EC was 447 ± 43% of that in SMC. The greater activity of NCX in EC than in SMC is consistent with the greater NCX1 protein abundance observed in Western blots in Fig. 4.

Bottom Line: Vascular endothelial cells (EC) and smooth muscle cells (SMC) require a decrease in cytoplasmic Ca2+ concentration after activation.Since the two cell types differ in their structure and function, we compared the activities of PMCA, NCX and SERCA in pig coronary artery EC and SMC, the types of isoforms expressed using RT-PCR, and their protein abundance using Western blots.PMCA, SERCA and NCX differ in their affinities for Ca2+ and regulation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada.

ABSTRACT
Vascular endothelial cells (EC) and smooth muscle cells (SMC) require a decrease in cytoplasmic Ca2+ concentration after activation. This can be achieved by Ca2+ sequestration by the sarco-/endoplasmic reticulum Ca2+ pumps (SERCA) and Ca2+ extrusion by plasma membrane Ca2+ pumps (PMCA) and Na+-Ca2+-exchangers (NCX). Since the two cell types differ in their structure and function, we compared the activities of PMCA, NCX and SERCA in pig coronary artery EC and SMC, the types of isoforms expressed using RT-PCR, and their protein abundance using Western blots. The activity of NCX is higher in EC than in SMC but those of PMCA and SERCA is lower. Consistently, the protein abundance for NCX protein is higher in EC than in SMC and those of PMCA and SERCA is lower. Based on RT-PCR experiments, the types of RNA present are as follows: EC for PMCA1 while SMC for PMCA4 and PMCA1; EC for SERCA2 and SERCA3 and SMC for SERCA2. Both EC and SMC express NCX1 (mainly NCX1.3). PMCA, SERCA and NCX differ in their affinities for Ca2+ and regulation. Based on these observations and the literature, we conclude that the tightly regulated Ca2+ removal systems in SMC are consistent with the cyclical control of contractility of the filaments and those in EC are consistent with Ca2+ regulation of the endothelial nitric oxide synthase near the cell surface. The differences between EC and SMC should be considered in therapeutic interventions of cardiovascular diseases.

Show MeSH
Related in: MedlinePlus