The α2 isoform of the Na,K-pump is important for intercellular communication, agonist-induced contraction, and EDHF-like response in rat mesenteric arteries

The specific role of different isoforms of the Na,K-pump in the vascular wall is still under debate. We have previously suggested that the α(2) isoform of the Na,K-pump (α(2)), Na(+), Ca(2+)-exchange (NCX), and connexin43 form a regulatory microdomain in smooth muscle cells (SMCs), which controls intercellular communication and contractile properties of the vascular wall. We have tested this hypothesis by downregulating α(2) in cultured SMCs and in small arteries with siRNA in vivo. Intercellular communication was assessed by using membrane capacitance measurements. Arteries transfected in vivo were tested for isometric and isobaric force development in vitro; [Ca(2+)](i) was measured simultaneously. Cultured rat SMCs were well-coupled electrically, but 10 μM ouabain uncoupled them. Downregulation of α(2) reduced electrical coupling between SMCs and made them insensitive to ouabain. Downregulation of α(2) in small arteries was accompanied with significant reduction in NCX expression. Acetylcholine-induced relaxation was not different between the groups, but the endothelium-dependent hyperpolarizing factor-like component of the response was significantly diminished in α(2)-downregulated arteries. Micromolar ouabain reduced in a concentration-dependent manner the amplitude of norepinephrine (NE)-induced vasomotion. Sixty percent of the α(2)-downregulated arteries did not have vasomotion, and vasomotion in the remaining 40% was ouabain insensitive. Although ouabain increased the sensitivity to NE in the control arteries, it had no effect on α(2)-downregulated arteries. In the presence of a low NE concentration the α(2)-downregulated arteries had higher [Ca(2+)](i) and tone. However, the NE EC50 was reduced under isometric conditions, and maximal contraction was reduced under isometric and isobaric conditions. The latter was caused by a reduced Ca(2+)-sensitivity. The α(2)-downregulated arteries also had reduced contraction to vasopressin, whereas the contractile response to high K(+) was not affected. Our results demonstrate the importance of α(2) for intercellular coupling in the vascular wall and its involvement in the regulation of vascular tone.

Medienart:	E-Artikel

Erscheinungsjahr:	2012
Erschienen:	2012

Enthalten in:	Zur Gesamtaufnahme - volume:303
Enthalten in:	American journal of physiology. Heart and circulatory physiology - 303(2012), 1 vom: 15. Juli, Seite H36-46

Sprache:	Englisch

Beteiligte Personen:	Matchkov, Vladimir V [VerfasserIn] Moeller-Nielsen, Nina [VerfasserIn] Dam, Vibeke Secher [VerfasserIn] Nourian, Zahra [VerfasserIn] Briggs Boedtkjer, Donna M [VerfasserIn] Aalkjaer, Christian [VerfasserIn]

Links:	Volltext

Themen:	Biological Factors Connexin 43 EC 7.2.2.13 Endothelium-dependent hyperpolarization factor Journal Article RNA, Small Interfering Research Support, Non-U.S. Gov't Sodium-Calcium Exchanger Sodium-Potassium-Exchanging ATPase Sodium-calcium exchanger 1

Anmerkungen:	Date Completed 04.09.2012 Date Revised 30.09.2020 published: Print-Electronic Citation Status MEDLINE

doi:	10.1152/ajpheart.00673.2011

funding:
Förderinstitution / Projekttitel:

PPN (Katalog-ID):	NLM217555667