Pflügers Archiv

, Volume 416, Issue 6, pp 727–734

Intracellular free calcium concentration / force relationship in rabbit inferior vena cava activated by norepinephrine and high K+

  • Raouf A. Khalil
  • Cornelis van Breemen
Heart, Circulation, Respiration and Blood; Environmental and Exercise Physiology

DOI: 10.1007/BF00370622

Cite this article as:
Khalil, R.A. & van Breemen, C. Pflügers Arch (1990) 416: 727. doi:10.1007/BF00370622


The changes in isometric force and the underlying fluctuations in intracellular free calcium concentration ([Ca2+]i) were monitored simultaneously in thin sheets of rabbit inferior vena cava loaded with the fluorescent Ca2+ indicator fura-2. In resting tissues bathed in physiological saline solution, the estimated [Ca2+]i was approximately 105 nM. The α-adrenergic agonist norepinephrine (10 μM) caused an initial rise in [Ca2+]i to 264 nM during force development, which dropped to 216 nM during force maintenance. The maintained norepinephrine-induced increase in force and [Ca2+]i was reversed in Ca2+-free (2 mM EGTA) solution. Membrane depolarization by high K+ (80 mM) significantly increased [Ca2+]i to 234 nM. Compared to norepinephrine, high K+ caused about the same steady-state increase in [Ca2+]i, but a smaller increase in force. [Ca2+]i/force curves were constructed at different concentrations of extracellular Ca2+, with either norepinephrine or high K+ as a stimulant. The curve generated with norepinephrine was located to the left of that generated with high K+.

Key words

Vascular smooth muscle Calcium 

Copyright information

© Springer-Verlag 1990

Authors and Affiliations

  • Raouf A. Khalil
    • 1
  • Cornelis van Breemen
    • 1
  1. 1.Department of PharmacologyUniversity of Miami School of MedicineMiamiUSA

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