Involvement of constitutive nitric oxide synthase in the portal-systemic collaterals of portal hypertensive rats

J Chin Med Assoc. 2005 Jun;68(6):245-9. doi: 10.1016/S1726-4901(09)70144-3.

Abstract

Background: Recent studies have shown that endothelial nitric oxide (NO) is involved in modulating the vascular response to vasoconstrictors in portal-systemic collaterals of portal hypertensive rats. This study investigated which isoform of NO synthase is involved in the collateral circulation of portal hypertensive rats.

Methods: The relaxation response to acetylcholine (10(-8) M, 10(-7) M and 10(-6) M) in norepinephrine (NE)-preconstricted portal-systemic collaterals was investigated after incubation with vehicle (Krebs solution), a preferential inducible NO synthase inhibitor (aminoguanidine [AG]), or a non-selective NO synthase inhibitor (Nomega-nitro-L-arginine [NNA]), in rats with partial portal vein ligation. Mean arterial pressure was measured before the perfusion experiments.

Results: Bodyweight and mean arterial pressure before the perfusion studies were similar in the vehicle, AG and NNA groups. Preincubation with NNA, but not AG, produced a significant increase in baseline perfusion pressure compared with the vehicle group (p < 0.05). The increase in perfusion pressure in response to NE was enhanced in the presence of NNA (p < 0.05), but not AG. In addition, preincubation with NNA, but not AG, significantly suppressed acetylcholine-induced relaxation in the portal-systemic collaterals (p < 0.05).

Conclusion: These results suggest that constitutive, rather than inducible, NO synthase is involved in the vascular response to vasoconstrictors in the portal-systemic collaterals of portal hypertensive rats.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcholine / pharmacology
  • Animals
  • Collateral Circulation / physiology*
  • Hypertension, Portal / physiopathology*
  • Male
  • Nitric Oxide / physiology
  • Nitric Oxide Synthase / physiology*
  • Nitroarginine / pharmacology
  • Portal System / physiopathology*
  • Rats
  • Rats, Sprague-Dawley
  • Vasodilation / drug effects

Substances

  • Nitroarginine
  • Nitric Oxide
  • Nitric Oxide Synthase
  • Acetylcholine