Endotoxin Concentrations Measured by a Chromogenic Assay in Portal and Peripheral Venous Blood in Ten Dogs With Portosystemic Shunts

Abstract

A chromogenic Limulus amebocyte lysate assay was used to measure portal and peripheral venous endotoxin concentrations in ten medically managed dogs undergoing surgery for correction of a single extrahepatic portosystemic shunt. In all dogs, both peripheral and portal venous blood samples were obtained at the time of surgical manipulation of the anomalous vessel. In six dogs, peripheral venous samples were obtained an average of 8.0 months after surgery. Five physically normal dogs without biochemical or histologic evidence of liver disease served as controls. Data analysis failed to demonstrate significant differences in peripheral and portal venous endotoxin concentrations between the control and study groups. Postoperatively five of six dogs showed a measurable reduction in peripheral venous endotoxin concentration over intraoperatively obtained values, but the differences were not statistically significant (P = 0.06). Based on results of this study it was concluded that systemic endotoxemia was not present in dogs with a single extrahepatic portosystemic shunt that were medically stable prior to surgery. (Journal of Veterinary Internal Medicine 1991; 571-74) ENDOTOXIN is a lipopolysaccharide constituent of the cell wall of gram-negative bacteria that is freed upon death of the organism.' Under normal circumstances endotoxins from intestinal bacteria are absorbed into the portal circulation but are then cleared by the hepatic reticuloendothelial system (RES).2-4 Results of several studies indicate that in the presence of experimentally induced or naturally occurring hepatic disease, systemic endotoxemia may e~i s t .~,~-'~ Endotoxin may be detected in clinical samples by complement activation, radioimmunoassay for O-antigen, and the Limulus amebocyte lysate (LAL) assay.'2-20 Of these available methods, the LAL assay is by far the most sensitive. By using a synthetic chromogenic substrate for the Limulus enzyme the LAL assay has the capability of detecting endotoxin at picogram concentrations.

Bacteriological study of the liver in dogs

“…The results suggest that the majority of adult healthy dogs harbour a bacterial population in the liver parenchyma, but a common pattern cannot be defined. It is known that under normal physiological conditions, the microbial population present in the liver is kept at levels compatible with a healthy status (ie, without resulting in infection) by the liver mononuclear phagocytic system, mainly represented by the Kupffer cells (Peterson andothers 1991, Center 1996). Conversely, in the presence of vascular compromise resulting in liver hypoxia, the existence of a bacterial population in the liver may elicit severe clinical symptoms (Bunch 2000).…”

Lipopolysaccharide and toll-like receptor 4 in dogs with congenital portosystemic shunts

“…Gram-negative 85 bacteria are present in the small intestine and therefore LPS is absorbed from the gut 86 and into the portal vein (Peterson et al, 1991;Howe et al, 1997). LPS has been 87 shown to play a positive role in liver regeneration in rodent models (Cornell, 1985a, 88 b, 1990; Gao et al, 1999).…”

The transhepatic endotoxin gradient is present despite liver cirrhosis and is attenuated after transjugular portosystemic shunt (TIPS).

“…For decades, there has been great interest in unraveling the pathophysiology of bacterial translocation in cirrhosis [3]. Experimental data derived from animal studies demonstrated portal and systemic bacteremia, predominantly Gram-negative organisms, in cirrhotic animals with portal hypertension [4-6]. Research conducted 20-30 years ago suggested an important role for endotoxemia in liver cirrhosis, but the assays available at that time were less sensitive and human portal blood sampling is challenging [6,7].…”

“…Experimental data derived from animal studies demonstrated portal and systemic bacteremia, predominantly Gram-negative organisms, in cirrhotic animals with portal hypertension [4-6]. Research conducted 20-30 years ago suggested an important role for endotoxemia in liver cirrhosis, but the assays available at that time were less sensitive and human portal blood sampling is challenging [6,7]. Recent detection of bacterial translocation during HIV infection, thought to result from increased gut permeability, provided a plausible cause of systemic immune activation; however, parallel studies in, HBV, HCV and HIV-HCV co-infection demonstrated that bacterial translocation is strongly associated with cirrhosis, raising questions of cause and effect [8-11].…”