A mathematical model of Ca2+ dynamics in rat mesenteric smooth muscle cell: agonist and NO stimulation

J Theor Biol. 2008 Jul 21;253(2):238-60. doi: 10.1016/j.jtbi.2008.03.004. Epub 2008 Mar 18.

Abstract

A mathematical model of calcium dynamics in vascular smooth muscle cell (SMC) was developed based on data mostly from rat mesenteric arterioles. The model focuses on (a) the plasma membrane electrophysiology; (b) Ca2+ uptake and release from the sarcoplasmic reticulum (SR); (c) cytosolic balance of Ca2+, Na+, K+, and Cl ions; and (d) IP3 and cGMP formation in response to norepinephrine(NE) and nitric oxide (NO) stimulation. Stimulation with NE induced membrane depolarization and an intracellular Ca2+ ([Ca2+]i) transient followed by a plateau. The plateau concentrations were mostly determined by the activation of voltage-operated Ca2+ channels. NE causes a greater increase in [Ca2+]i than stimulation with KCl to equivalent depolarization. Model simulations suggest that the effect of[Na+]i accumulation on the Na+/Ca2+ exchanger (NCX) can potentially account for this difference.Elevation of [Ca2+]i within a concentration window (150-300 nM) by NE or KCl initiated [Ca2+]i oscillations with a concentration-dependent period. The oscillations were generated by the nonlinear dynamics of Ca2+ release and refilling in the SR. NO repolarized the NE-stimulated SMC and restored low [Ca2+]i mainly through its effect on Ca2+-activated K+ channels. Under certain conditions, Na+-K+-ATPase inhibition can result in the elevation of [Na+]i and the reversal of NCX, increasing resting cytosolic and SR Ca2+ content, as well as reactivity to NE. Blockade of the NCX's reverse mode could eliminate these effects. We conclude that the integration of the selected cellular components yields a mathematical model that reproduces, satisfactorily, some of the established features of SMC physiology. Simulations suggest a potential role of intracellular Na+ in modulating Ca2+ dynamics and provide insights into the mechanisms of SMC constriction, relaxation, and the phenomenon of vasomotion. The model will provide the basis for the development of multi-cellular mathematical models that will investigate microcirculatory function in health and disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium Channels / physiology
  • Membrane Potentials / physiology
  • Mesentery / blood supply
  • Microcirculation / drug effects
  • Microcirculation / physiology
  • Muscle, Smooth, Vascular / cytology
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / metabolism*
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / metabolism*
  • Nitric Oxide / pharmacology
  • Potassium Channels, Calcium-Activated / physiology
  • Potassium Channels, Voltage-Gated / physiology
  • Proteins / pharmacology
  • Rats
  • Ryanodine Receptor Calcium Release Channel / metabolism
  • Sarcoplasmic Reticulum / metabolism

Substances

  • ATPase inhibitory protein
  • Calcium Channels
  • Potassium Channels, Calcium-Activated
  • Potassium Channels, Voltage-Gated
  • Proteins
  • Ryanodine Receptor Calcium Release Channel
  • Nitric Oxide
  • Calcium