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Nitric oxide modulates hepatic vascular tone in normal rat liver
M K Mittal1, T K Gupta, F Y Lee
1Hepatic Hemodynamic Laboratory, Veterans Affairs Medical Center, West Haven 06516.
The American Journal of Physiology
|September 1, 1994
Summary
Nitric oxide (NO) helps regulate blood pressure in rat livers. Inhibiting NO increased pressure and sensitivity to norepinephrine, suggesting NO
Area of Science:
- Physiology
- Pharmacology
Background:
- The role of nitric oxide (NO) in regulating intrahepatic portal circulation is not fully understood.
- Vascular tone and responsiveness to vasoactive agents are critical in liver hemodynamics.
Purpose of the Study:
- To investigate the role of nitric oxide (NO) in the intrahepatic portal circulation of normal rat livers.
- To determine if NO modulates the vascular response to norepinephrine (NE) in the rat liver.
Main Methods:
- In situ liver perfusion in rats.
- Administration of N omega-nitro-L-arginine (NNA), a specific NO biosynthesis inhibitor.
- Measurement of portal pressure and perfusate flow.
- Concentration-effect curves for norepinephrine (NE) in the presence and absence of NNA and L-arginine.
- In vivo intraportal infusion of NNA.
Main Results:
- N omega-nitro-L-arginine (NNA) significantly increased baseline portal pressure.
- NNA markedly enhanced the vasoconstrictive response to norepinephrine (NE).
- The effect of NNA was reversed by L-arginine, and in vivo infusion of NNA also increased portal pressure.
Conclusions:
- Nitric oxide (NO) contributes to basal vascular tone in the rat intrahepatic portal circulation.
- NO attenuates the vascular response to norepinephrine (NE) in this vascular bed.
- These findings support a functional role for NO in regulating rat intrahepatic portal hemodynamics.