Dissecting out the complex Ca2+-mediated phenylephrine-induced contractions of mouse aortic segments

PLoS One. 2015 Mar 24;10(3):e0121634. doi: 10.1371/journal.pone.0121634. eCollection 2015.

Abstract

L-type Ca2+ channel (VGCC) mediated Ca2+ influx in vascular smooth muscle cells (VSMC) contributes to the functional properties of large arteries in arterial stiffening and central blood pressure regulation. How this influx relates to steady-state contractions elicited by α1-adrenoreceptor stimulation and how it is modulated by small variations in resting membrane potential (Vm) of VSMC is not clear yet. Here, we show that α1-adrenoreceptor stimulation of aortic segments of C57Bl6 mice with phenylephrine (PE) causes phasic and tonic contractions. By studying the relationship between Ca2+ mobilisation and isometric tension, it was found that the phasic contraction was due to intracellular Ca2+ release and the tonic contraction determined by Ca2+ influx. The latter component involves both Ca2+ influx via VGCC and via non-selective cation channels (NSCC). Influx via VGCC occurs only within the window voltage range of the channel. Modulation of this window Ca2+ influx by small variations of the VSMC Vm causes substantial effects on the contractile performance of aortic segments. The relative contribution of VGCC and NSCC to the contraction by α1-adrenoceptor stimulation could be manipulated by increasing intracellular Ca2+ release from non-contractile sarcoplasmic reticulum Ca2+ stores. Results of this study point to a complex interactions between α1-adrenoceptor-mediated VSMC contractile performance and Ca2+ release form contractile or non-contractile Ca2+ stores with concomitant Ca2+ influx. Given the importance of VGCC and their blockers in arterial stiffening and hypertension, they further point toward an additional role of NSCC (and NSCC blockers) herein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Aorta / physiology*
  • Calcium / metabolism*
  • Calcium Channels, L-Type / metabolism
  • Membrane Potentials
  • Mice
  • Mice, Inbred C57BL
  • Models, Biological*
  • Muscle Contraction / physiology*
  • Muscle, Smooth, Vascular / metabolism*
  • Muscle, Smooth, Vascular / physiology
  • Myography / methods
  • Phenylephrine / metabolism*
  • Receptors, Adrenergic, alpha-1 / metabolism

Substances

  • Calcium Channels, L-Type
  • Receptors, Adrenergic, alpha-1
  • Phenylephrine
  • Calcium

Grants and funding

Research was funded by the University of Antwerp. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.