Konomu Hirao

GLP-1 receptor antagonist as a potential probe for pancreatic β-cell imaging

We examined exendin(9-39), an antagonist of glucagon-like peptide-1 (GLP-1) receptor (GLP-1R), as a potential probe for imaging of pancreatic beta-cells. To evaluate in vitro receptor specificity, binding assay was performed using dispersed mouse islet cells. Binding assay showed competitive inhibition of [(125)I]BH-exendin(9-39) binding by non-radioactive exendin(9-39). To assess in vivo selectivity, the biodistribution was evaluated by intravenous administration of [(125)I]BH-exendin(9-39) to mice. Radioactivity of harvested pancreas reached highest levels at 60 and 120min among organs examined except lung. Pre-administration of excess non-radioactive exendin(9-39) remarkably and specifically blocked the radioactivity of pancreas. After [(125)I]BH-exendin(9-39) injection into transgenic mice with pancreatic beta-cells expressing GFP, fluorescent and radioactive signals of sections of pancreas were evaluated with an image analyzer. Imaging analysis showed that the fluorescent GFP signals and the radioactive signals were correspondingly located. Thus, the GLP-1R antagonist exendin(9-39) may serve as a useful probe for pancreatic beta-cell imaging.

Intraoperative measurement of the graft oxygenation state in living related liver transplantation by near infrared spectroscopy

Abstract Graft oxygenation plays an important role in successful liver transplantation. Intraoperative changes in the oxygenation state of the liver graft were measured by near infrared spectroscopy in 28 cases of living related liver transplantation. Oxygen saturation of hemoglobin in the liver (hepatic SO2) changed from 81.2%± 1.5% (mean ± SEM) before donation (in the donor) to 49.7%± 4.2% after portal reflow, to 58.4%± 5.0% after arterial reflow, and then to 71.4%± 3.9% before closure. Mean hepatic SO2 was positively correlated with portal flow rate as measured by duplex Doppler sonography. Cases with low portal flow rate showed a high coefficient of variation (SD/mean) of hepatic SO2, indicating heterogeneous tissue oxygenation. Though graft size was expected to affect the graft oxygenation state, hepatic SO2 was fairly independent of the graft‐to‐recipient weight ratio. In two cases with markedly low hepatic SO2, postoperative graft dysfunction occurred. This study suggest that the method of near infrared spectroscopy is reliable and useful for assessing the graft oxygenation state in liver transplantation.

Delayed oxidation of intramitochondrial pyridine nucleotide oxidoreduction state as compared with tissue oxygenation in human liver transplantation

Intra- and post-operative oxygenation of graft liver and subsequent oxidation of the intramitochondrial oxido-reduction state of pyridine nucleotide were studied in partial liver transplantation from living related donors with the ratio of acetoacetate to beta-hydroxybutyrate in arterial blood (AKBR), the ratio of oxidized flavoprotein to reduced pyridine nucleotide (FP/PN ratio) and oxygen saturation of hemoglobin in liver tissue (hepatic SO2). Decreased hepatic SO2 and its heterogenous distribution after reflow of portal vein and hepatic artery were normalized by the end of operation, while the intramitochondrial oxido-reduction state was still reduced at the end of operation and was normalized only at 24 h after the operation. The observed delay in oxidation of the intramitochondrial oxido-reduction state as compared with tissue oxygenation indicates the transition of the intramitochondrial oxido-reduction state associated with the initiation of metabolic activity from the cold preserved state, and suggests an important role for microcirculation in the normalization of the oxido-reduction state.

Interrelationship of Oxygen Supply by Hepatic Artery and Portal Vein: Rapid Analysis of Ischemia-Reflow-Induced Changes in Hepatic Oxygenation in Experimental and Clinical Subjects by Tissue Near-Infrared Spectroscopy

The rapid changes in extracellular oxygenation and intracellular oxidation during ischemia and reflow were measured in deep liver tissue by a novel method combining tissue near-infrared spectroscopy with multicomponent curve-fitting analysis. This method enabled us to make real-time measurements of oxygen saturation (SO2) and amount (THB) of hemoglobin in the liver sinusoid as parameters of extracellular oxygenation state and of redox transition of cytochrome aa3 as intracellular oxidation state. Clamping of the hepatic artery in rabbit decreased the THB with a transient fall of SO2. Clamping of the portal vein decreased both SO2 and THB. The decreases of SO2 and THB caused by Pringles maneuver were larger than the sum of decreases by hepatic artery and portal vein. These changes in SO2 were correlated with intramitochondrial oxidation state as measured by cytochrome aa3. These results indicate the presence of an interrelationship of oxygen supply by hepatic artery and portal vein. This method was clinically applied during and after clamping of hepatic artery and portal vein in 19 cases of hepatic resection with or without chronic hepatic diseases. The decrease in SO2 values before and after clamping (SO2D) and the slope of SO2 recovery (SO2R) after release were calculated. SO2D and SO2R values of the portal vein in cirrhotics were significantly higher and lower, respectively, than those in the normal liver. These data indicate that the present method provides a rapid and reliable method of quantifying hepatic oxygenation during liver surgery and its perioperative management.