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Morphine attenuates microvascular hyperpermeability via a protein kinase A-dependent pathway

Rudolph Puana1, Russell K McAllister, Felicia A Hunter

  • 1Department of Anesthesiology, Scott and White Clinic and Memorial Hospital, Scott, Sherwood and Brindley Foundation, Texas A&M Health Science Center College of Medicine, Temple, Texas 76508, USA.

Anesthesia and Analgesia
|January 30, 2008
PubMed
Abstract

Insights

Morphine sulfate (MS) reduces vascular hyperpermeability by activating endothelial cell mu receptors, increasing cyclic adenosine monophosphate (cAMP) and inhibiting key signaling pathways. This mechanism is crucial for managing shock-induced vascular leakage.

Area of Science:

  • Physiology
  • Pharmacology
  • Cell Biology

Background:

  • Previous studies show morphine sulfate (MS) attenuates microvascular hyperpermeability post-hemorrhagic shock.
  • MS interacts with mu receptors on endothelial cells, which are known to activate adenylate cyclase.
  • This activation elevates cyclic adenosine monophosphate (cAMP) levels, potentially inhibiting the phosphoinositide/MAP kinase pathway.

Purpose of the Study:

  • To investigate the role of adenylate cyclase and protein kinase A (PKA) in MS-mediated attenuation of vascular hyperpermeability.
  • To determine if MS acts upstream of PKA in regulating endothelial cell permeability.

Main Methods:

  • Experiments were conducted on urethane-anesthetized Sprague-Dawley rats.
  • Groups received either a control, adenylate cyclase inhibitor (SQ22536), PKA inhibitor (H89), or MS with/without inhibitors.
  • Vascular permeability was assessed using intravital microscopy and rat lung microvascular endothelial cell monolayers.

Main Results:

  • Inhibition of adenylate cyclase or PKA led to increased vascular hyperpermeability.
  • MS treatment attenuated the hyperpermeability caused by adenylate cyclase inhibition.
  • MS failed to attenuate hyperpermeability when PKA was inhibited.

Conclusions:

  • The findings support the hypothesis that MS increases cAMP via adenylate cyclase activation.
  • MS attenuates vascular hyperpermeability through a PKA-dependent mechanism.
  • MS acts upstream of PKA, highlighting a novel signaling pathway in vascular permeability regulation.

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