Abstract
In the present study, we determined the vascular functions using a canine model of isolated intestinal segment perfused with constant flow. The effects of an NO donor, S-nitroso- N-acetylpenicillamine (SNAP) and an NO synthase inhibitor, N ω-nitro- l-arginine methyl ester ( l-NAME) on the vascular factors (resistance, exchange and capacitance) were evaluated. In condition of venous pressure at 0 mmHg, we determined and calculated arterial pressure (Pa) and capillary pressure (Pc). Vascular factors including total, pre- and post-capillary resistance ( R T, Ra and Rv), vascular compliance (VC) and capillary filtration coefficient ( K fc) were obtained. SNAP at doses 10 − 6 to 10 − 4 mol/l produced vasodilatory effects. It dose-dependently reduced the Pa, Pc, R T and Ra, as well as the Ra/Rv ratio. The Rv was slightly decreased. This agent increased the vascular capacity, VC and K fc. NO inhibition with l-NAME (10 − 6 to 10 − 4 mol/l) produced the opposite effects. The vasoconstrictory effects of l-NAME increased Pa, Pc, R T and Ra as well as the Ra/Rv ratio. It slightly raised the Rv. l-NAME reduced the vascular capacity, VC and K fc. The effects of l-NAME were also dose-dependent. This study has provided a detailed data of the vasodilatory and vasoconstrictory effects NO donation and inhibition on vascular factors in the intestinal vasculature.
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