Nitric Oxide and Prostacyclin in Ultrasonic Vasodilatation of the Canine Internal Mammary Artery

Ann Thorac Surg. 2004 Jan;77(1):126-32. doi: 10.1016/s0003-4975(03)01293-1.

Abstract

Background: Investigators recently demonstrated increased free blood flow from radial artery free grafts harvested using ultrasonic technology. We investigated the mechanism underlying this phenomenon.

Methods: Canine internal mammary artery segments (with and without intact endothelium) were precontracted with norepinephrine and sonicated 3 seconds in organ chambers with ultrasonic coagulating shears (Harmonic Scalpel; Ethicon Endo-Surgery, Cincinnati, OH) functioning at level 2. Vessel tension was continuously measured to examine vasoactivity in response to sonication alone (control) or with N(ù)-Nitro-l-arginine (l-NNA) and indomethacin added to the chamber medium individually or in combination. Tissue heating, acoustic pressure, and endothelial damage as detected by scanning electron micrography were also assessed.

Results: In vitro sonication with the Harmonic Scalpel induced predominately endothelium-dependent internal mammary artery vasorelaxation but a small endothelium-independent contribution was also observed. Early vasorelaxation (1 minute after stimulus) was maximally inhibited by l-NNA alone and in combination with indomethacin. Relaxation during this period was insignificantly affected by indomethacin alone. Only the combination of l-NNA and indomethacin maximally inhibited late vasorelaxation (5 minutes after stimulus), whereas inhibitory effects of l-NNA diminished during this time period. Indomethacin inhibited relaxation substantially during this phase, although significantly less than did l-NNA alone. The Harmonic Scalpel minimally heated the tissue surface (0.3 +/- 0.03 degrees C) and did not disrupt endothelial cell integrity while operating at 50 mW/cm(2) intensity (acoustic pressure 40 kPa).

Conclusions: Sonication induces vasorelaxation almost completely by time-dependent endothelial nitric oxide and prostacyclin release, which appears unrelated to tissue heating or endothelial architectural disruption.

MeSH terms

  • Animals
  • Dogs
  • Epoprostenol / pharmacology*
  • Female
  • Male
  • Mammary Arteries / drug effects*
  • Mammary Arteries / physiology*
  • Nitric Oxide / pharmacology*
  • Ultrasonics
  • Vasodilation / drug effects*

Substances

  • Nitric Oxide
  • Epoprostenol