The aim of this study was to develop a method for the quantification of hepatobiliary uptake and secretion of conjugated bile acids with PET and the 11 C-labeled conjugated bile acid analog [N-methyl-11 C] cholylsarcosine ( 11 C-CSar). Methods: Six pigs (13 experiments) underwent dynamic 11 C-CSar PET of the liver with simultaneous measurements of hepatic blood perfusion and 11 C-CSar concentrations in arterial, portal, and hepatic venous blood. In 3 pigs (7 experiments), bile was collected from a catheter in the common hepatic duct. PET data were analyzed with a 2-tissue compartmental model with calculation of rate constants for the transport of 11 C-CSar among blood, hepatocytes, and intra-and extrahepatic bile ducts. PET results were validated against invasive blood and bile measurements. Results: The directly measured rate of secretion of 11 C-CSar into bile was equal to the rate of removal from blood at steady state. Accordingly, hepatocytes did not accumulate bile acids but simply facilitated the transport of bile acids from blood to bile against a measured concentration gradient of 4,000. The rate constant for the secretion of 11 C-CSar from hepatocytes into bile in experiments with a catheter in the common hepatic duct was 25% of that in experiments without a catheter (P , 0.05); we interpreted this result to be mild cholestasis caused by the catheter. The catheter caused an increased backflux of 11 C-CSar from hepatocytes to blood, and hepatic blood flow was 25% higher than in experiments without the catheter. The capacity for the overall transport of 11 C-CSar from blood to bile, as quantified by intrinsic clearance, was significantly lower in experiments with the catheter than in those without the catheter (P , 0.001). PET and blood measurements correlated significantly (P , 0.05). Conclusion: The in vivo kinetics of hepatobiliary secretion of conjugated bile acids can now be determined by dynamic 11 C-CSar PET.
Seventy percent partial hepatectomy in healthy rats induces a rapid regenerative response and PODs 2, 4 and 8 seems optimal for assessing hepatic growth in future studies.
BackgroundIschemic pre- and postconditioning protects the liver against ischemia/reperfusion injuries. The aim of the present study was to examine how ischemic pre- and postconditioning affects gene expression of hypoxia inducible factor 1α (HIF-1α), vascular endothelial growth factor A (VEGF-A) and transforming growth factor β (TGF-β) in liver tissue.Methods28 rats were randomized into five groups: control; ischemia/reperfusion; ischemic preconditioning (IPC); ischemic postconditioning (IPO); combined IPC and IPO. IPC consisted of 10 min of ischemia and 10 min of reperfusion. IPO consisted of three cycles of 30 sec. reperfusion and 30 sec. of ischemia.ResultsHIF-1α mRNA expression was significantly increased after liver ischemia compared to controls (p = 0.010). HIF-1α mRNA expression was significantly lower in groups subjected to IPC or combined IPC and IPO when compared to the ischemia/reperfusion group (p = 0.002). VEGF-A mRNA expression increased in the ischemia/reperfusion or combined IPC and IPO groups when compared to the control group (p < 0.05).ConclusionIschemic conditioning seems to prevent HIF-1α mRNA induction in the rat liver after ischemia and reperfusion. This suggests that the protective effects of ischemic conditioning do not involve the HIF-1 system. On the other hand, the magnitude of the HIF-1α response might be a marker for the degree of I/R injuries after liver ischemia. Further studies are needed to clarify this issue.
Circulating liver enzymes such as alanine transaminase are often used as markers of hepatocellular damage. Ischaemia/reperfusion (I/R) injury is an inevitable consequence of prolonged liver ischaemia. The aim of this study was to examine the correlation between liver enzymes and volume of liver cell necrosis after ischaemia/reperfusion injuries, using design-unbiased stereological methods. Forty-seven male Wistar rats were subjected to 1 h of partial liver ischaemia, followed by either 4 or 24 h of reperfusion. Within each group, one-third of animals were subjected to ischaemic preconditioning and one-third to ischaemic postconditioning. At the end of reperfusion, blood and liver samples were collected for analysis. The volume of necrotic liver tissue was subsequently correlated to circulating markers of I/R injury. Correlation between histological findings and circulating markers was performed using Pearson's correlation coefficient. Alanine transferase peaked after 4 h of reperfusion; however, at this time-point, only mild necrosis was observed, with a Pearson's correlation coefficient of 0.663 (P = 0.001). After 24 h of reperfusion, alanine aminotransferase was found to be highly correlated to the degree of hepatocellular necrosis R = 0.836 (P = 0.000). Furthermore, alkaline phosphatase (R = 0.806) and α-2-macroglobulin (R = 0.655) levels were also correlated with the degree of necrosis. We show for the first time that there is a close correlation between the volume of hepatocellular necrosis and alanine aminotransferase levels in a model of I/R injury. This is especially apparent after 24 h of reperfusion. Similarly, increased levels of alkaline phosphatase and α-2-macroglobulin are correlated to the volume of liver necrosis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.