Minor involvement of nitric oxide during chronic endotoxemia in anesthetized pigs

Abstract

Pastor, Catherine M., Antoine Hadengue, and Andreas K. Nussler. Minor involvement of nitric oxide during chronic endotoxemia in anesthetized pigs. Am. J. Physiol. Gastrointest. Liver Physiol. 278: G416-G424, 2000.-To study the modifications of hepatic blood flow and hepatic function over time during endotoxemia, 10 pigs received a continuous intravenous infusion of endotoxin (Endo, 160 ng · kg Ϫ1 ·h Ϫ1 ) over 18 h and 7 control (Ctrl) animals received a saline infusion. The involvement of nitric oxide (NO) in this endotoxic model was assessed by measuring plasma concentrations of NO 2 Ϫ , NO 3 Ϫ , and cGMP, by testing vascular reactivity to ACh, and by evaluating inducible NO synthase (NOS 2) expression in hepatic biopsies. Endotoxin induced hypotensive and normokinetic shock in association with few modifications of hepatic blood flow, and hepatic injury was observed in both groups. Endotoxin did not increase plasma concentrations of NO 2 Ϫ , NO 3 Ϫ , and cGMP. The ACh-dependent decrease of mean arterial pressure was reduced in Endo pigs, whereas a minor difference was observed between Ctrl and Endo pigs for ACh-dependent modification of hepatic perfusion. Hepatic NOS 2 mRNA was not detected in Ctrl pigs. In Endo pigs, NOS 2 protein expression was detected only in tissues surrounding the portal vein and the inferior vena cava, whereas NOS 2 mRNA was expressed in all hepatic biopsies. Thus, although endotoxemia induces NOS 2 expression in the liver, our findings show that NO involvement is lower in pigs than in rodents during endotoxemia. liver; vascular reactivity; acetylcholine; inducible nitric oxide synthase; hepatic circulation SEPTIC SHOCK, which remains an important cause of death in intensive care units, is characterized by hypotension, vascular hyporeactivity to vasoactive agents, myocardial dysfunction, and altered regional blood flows (4, 25). The multiple-organ dysfunction syndrome, which is defined as two or more organs failing at the same time, frequently occurs and is associated with a high mortality rate. Endotoxin, which is included in the wall of Gram-negative bacteria, is responsible for most of the abnormalities observed in sepsis and is commonly used to mimic septic shock in experimental models.The liver is crucial in severe sepsis because it contains most of the macrophages of the body (Kupffer cells) able to clear endotoxin and bacteria that may stimulate the systemic inflammatory response. Moreover, hepatocytes synthesize the acute-phase proteins and enzymes necessary to modulate the inflammatory response. Finally, because hepatic blood flow represents 25% of cardiac output (CO), modifications of hepatic perfusion may greatly interfere with systemic hemodynamics.Nitric oxide (NO) is one of the major mediators that induce cardiovascular abnormalities during septic shock. Under physiological conditions, the constitutive endothelial isoform of NO synthase (eNOS or NOS 3) produces low levels of NO and regulates vascular tone as well as numerous cell functions (24). In contrast, during sepsis,...

Effect of combining nicotinamide as a PARS-inhibitor with selective iNOS blockade during porcine endotoxemia

“…In fact, measuring the blood concentrations of the stable NO metabolites, namely NO 2 -and NO 3 -, may not be appropriate to estimate NO production in larger animals, in particular in pigs. Pastor et al [22] found no correlation between the NO production and the changes of plasma NO 2 /NO 3 levels either. This discrepancy may be due to marked changes in the total volume of distribution resulting from interstitial edema and flux into the third space, such as ascites [23].…”

“…# designates significant differences versus baseline (P<0.05), § designates significant differences 1400W+NAD versus CON group stored blood pressure to baseline levels without affecting the cardiac output or regional hemodynamics and attenuated the detrimental consequences of endotoxin on intestinal and hepatic energy balance. In our model, the timing of treatment intervention was initiated 12 h after onset of LPS infusion to establish hyperdynamic circulation with concomitant signs of metabolic alterations, thereby closely mimicking the clinical situation, and allowing sufficient time for upregulation of iNOS expression [22]. It is still difficult to estimate the time and the quantity of NO production in larger animals.…”

“…It is still difficult to estimate the time and the quantity of NO production in larger animals. According to the time necessary for iNOS expression, Pastor et al [22] recently reported direct evidence for in vivo iNOS protein in the liver of pigs as early as 6 h after starting LPS. Strikingly, we found a clear difference between the response of expired NO and that of plasma nitrate levels in the present study.…”

Heme oxygenase-1 protects human hepatocytes in vitro against warm and cold hypoxia

“…Total RNA was extracted from cultured hepatocytes as recently described [25]. Reverse transcription of total RNA to cDNA was carried out following a standard procedure and cDNA was amplified to detect HO-1 mRNA using specific primers based on the human HO-1 sequence: antisense 5 0 -TGC GGT GCA GCT CTT CTG-3 0 , sense 5-0 GCA ACC CGA CAG CAT GC-3 0 , amplifying a 244 bp product at cycles 35 [26].…”

Hyperthermia decreases the response to vasoconstrictors in rat portal veins

“…In experimental septic shock, an impaired response to vasoconstrictors is also observed in various regional circulations. In anesthetized pigs infused with endotoxin, we previously showed that the renal circulation was hyporesponsive to norepinephrine (Pastor, 1999), whereas the response of the hepatic circulation was not modified (Mastrangelo and Pastor, 1999;Pastor et al, 2000).…”