Background: Nitric oxide (NO) has been proposed to participate in the vascular hyporesponsiveness to vasopressin and its long-acting analogue glypressin during hemorrhage in portal hypertensive states. This study surveyed the role of NO regarding splanchnic hyporeactivity to glypressin and NO synthases (NOS) expression in different vascular beds in bleeding portal-hypertensive rats.
Methods: Under general anesthesia with ketamine, partially portal vein-ligated male Sprague-Dawley rats without or with bleeding were used to investigate the hemodynamic effects of glypressin (0.07 mg/kg intravenously) and constitutive (cNOS) and inducible NOS (iNOS) mRNA expression over the abdominal aorta and superior mesenteric artery.
Results: Splanchnic hyposensitivity to glypressin was noted in the hemorrhage-transfused rats with enhanced cNOS expression of superior mesenteric artery. No significant differences of cNOS and iNOS expression in abdominal aorta and iNOS in superior mesenteric artery were found between the with-bleeding and without-bleeding groups.
Conclusions: In rats with portal hypertension and acute hemorrhage, cNOS over-expression in superior mesenteric artery may take a part in the splanchnic hyposensitivity to glypressin.