Function and expression of ryanodine receptors and inositol 1,4,5‐trisphosphate receptors in smooth muscle cells of murine feed arteries and arterioles

Abstract

Key points• Feed arteries and arterioles, respectively, control the magnitude and distribution of blood flow to skeletal muscle but regional differences in the regulation of vasomotor tone are poorly understood.• To provide this insight, we investigated functional roles and molecular expression of the calcium-release channels, ryanodine receptors (RyRs) and inositol 1,4,5-trisphosphate receptors (IP 3 Rs) in smooth muscle cells (SMCs) of isolated pressurized vessels of mice.• In feed arteries, SMCs displayed localized calcium sparks and more global calcium waves. In arterioles, SMCs exhibited only calcium waves.• Calcium signalling and vasomotor tone were governed by both RyRs and IP 3 Rs in feed arteries, while only IP 3 Rs were functional in arterioles. Regional differences were also manifest in the expression profile of RyR isoforms.• This new perspective offers the potential for developing novel strategies to target therapeutic interventions to selective regions of vascular beds.Abstract We tested the hypothesis that vasomotor control is differentially regulated between feed arteries and downstream arterioles from the cremaster muscle of C57BL/6 mice.

Basal activity of voltage-gated Ca2+ channels controls the IP3-mediated contraction by α1-adrenoceptor stimulation of mouse aorta segments

“…Moreover, complex interactions between contractile and non-contractile stores occur (Flemming et al, 2002). Also species (Karaki et al, 1997) and blood vessel size (Westcott et al, 2012) matter for Ca 2 þ signaling in the in vitro preparation. All these observations preclude the extrapolation of SR/ER Ca 2 þ release and uptake data obtained in isolated or cultured VSMCs to the multicellular in vitro preparations (Flores-Soto et al, 2013).…”

Aging increases capacitance and spontaneous transient outward current amplitude of smooth muscle cells from murine superior epigastric arteries

“…The vessels were tested for leaks by pressurization to 80 cmH2O with no flow through the lumen while immersed in Dissection Solution to obtain maximal diameter and adjust their length to approximate that in situ. If the vessels were leak-free, then transmural pressure was reduced to 20 cmH 2O and they were superfused with Ca 2ϩ -containing PSS, warmed to 37°C and internal diameter measured (9,22,49,50). Only leak-free vessels were studied; no other selection criteria were applied.…”

“…The inclusion of sodium nitroprusside and diltiazem in this solution helped to maintain SMCs in a relaxed state during dissection and subsequent enzymatic isolation; their actions are reversible and without subsequent effect on ionic currents and vascular reactivity (23). Individual SEAs were hand-dissected while viewing through a stereomicroscope as described (49), cleaned of connective tissue and fat, and cut into segments 400 -800 m long.…”

“…Linearity and efficiency (E) of amplification for each gene product were verified by creating standard curves, plotting the critical threshold (CT) versus log of the dilution of cDNA. Efficiency-normalized relative abundance (40) was determined for BK␣ and BK␤1 using Gusb as the reference transcript and was computed as (EGusb CT /Etarget CT ) as described (49).…”

“…However, as shown in resistance networks of the mouse and hamster cremaster muscles, the regulation of BK Ca in arterioles differs from that in feed arteries (49,50), and it is unknown how aging affects BK Ca function in SMCs of skeletal muscle feed arteries. A recent study of endothelial tubes freshly isolated from murine superior epigastric arteries (SEAs) suggests that aging increased the function of endothelial K Ca (4).…”