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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, METHODS, RESULTS. Meshes: Animals, Arginine, Hemodynamics, Hypertension, Portal, Male, Mesentery, Nitric Oxide, Nitroarginine, Perfusion, Portal System, Rats, Rats, Sprague-Dawley.
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Does administration of N omega-nitro-L-arginine ameliorate portal-systemic shunting in portal-hypertensive rats? Context: Nitric oxide, a vasodilator synthesized from L-arginine by vascular endothelial cells, may play a role in the development of portal-systemic collaterals. This study investigated the effect of long-term inhibition of NO secretion on portal systemic shunting. Systemic and splanchnic hemodynamics and the degree of portal-systemic shunting were evaluated in partial portal vein-ligated rats after administration of placebo (0.9% saline) or N omega-nitro-L-arginine (NNA) (approximately 2 micrograms.kg-1 x min-1) intravenously for 6 days. NNA treatment induced increases in splanchnic arterial resistance (P < 0.001) and portal-collateral resistance (P < 0.05) and a decrease in portal venous inflow (P < 0.05). Portal pressure was not changed (NS). The splenic-systemic shunting was significantly decreased from 81% +/- 5% in the placebo-treated group to 69% +/- 4% in the NNA-treated group (P < 0.05), paralleled by an insignificant reduction in the mesenteric-systemic shunting (64% +/- 7% vs. 50% +/- 6%, NS). The attenuation of portal-systemic shunting by NNA was further shown by an increase in the vascular resistance of portal-systemic collateral venous bed using an in situ portal-systemic collateral perfusion model (1.27 +/- 0.05 vs. 1.07 +/- 0.03 cm H2O.mL-1 x min-1; P < 0.001).
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The results show that in portal hypertensive rats, NNA reduces portal-systemic shunting without reducing portal pressure, suggesting that NO plays a role in the collateralization of the portal system. In addition, high flow through the portal-collateral bed is probably an important driving force that is independent of portal hypertension for the development of portal-systemic shunting in portal-hypertensive rats. Final Decision: yes