Journal of cardiovascular pharmacology
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J. Cardiovasc. Pharmacol. · Sep 1998
Evidence for constitutive release of nitric oxide in the venous circuit of pigs.
To determine whether the venous circuit constitutively produces nitric oxide (NO), we infused the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) into anesthetized and mechanically ventilated pigs and measured venous circuit parameters. We measured cardiac output (Q) by thermodilution and obtained arterial (Part), central venous pressure (in the inferior vena cava), right atrial (Pra), pulmonary artery (PAP), and pulmonary capillary wedge pressures. A balloon was transiently inflated in the right atrium to stop venous return and obtain mean circulatory filling pressure (MCFP). ⋯ The increase in RVR of 167% from 1.8+/-0.6 mm Hg/L/min at baseline to 5.4+/-3.7 mm Hg/L/min (p < 0.05) was similar to the 188% increase in systemic vascular resistance. These data indicate that constitutive release of NO decreases baseline venous resistance and increases capacitance. There also appears to be a worsening of cardiac function when NOS is inhibited.