Duration of the hemodynamic effects of NG-nitro-L-arginine methyl ester in vivo

The objective of this study was to quantify the duration of the hemodynamic activity of N-G-nitro-L-arginine methyl ester (L-NAME) in a variety of different tissues following a single bolus injection of this nitric oxide synthase inhibitor to healthy rats. L-NAME (15 mu mol.kg(-1)) was injected (ip) into rats to produce maximal inhibition of endothelial cell NOS. Animals were subsequently anesthetized and blood flow was quantified using the radioactive microsphere/reference organ technique. At 1 h following a single bolus injection of L-NAME blood flow was reduced to the entire gastrointestinal tract, pancreas, and liver. Three hours following L-NAME administration, blood flow to the stomach and upper small intestine had returned to pretreatment levels; however, blood flow to the jejunum, ileal-jejunal junction, and colon remained significantly reduced. Splenic blood flow was significantly reduced and hepatic arterial blood flow was further reduced at this time as well. After 6 h following L-NAME administration, blood flow in all organs had completely recovered to control levels. Although cardiac index and total peripheral resistance had also returned to preinjection values at this time, mean arterial pressure remained elevated at 6 h posttreatment. Blood flow to the brain, lungs, and psoas muscle were unaffected by L-NAME administration at any time point. Taken together, these data demonstrate a differential regulation of vascular tone by NO in different vascular beds and, depending upon the organ system in question, the vasoactive activity of L-NAME may last from 3 to 6 h following a single bolus injection of this NOS inhibitor. (C) 2000 Academic Press.