Ketone body ratios of the superior and inferior vena cava and of pulmonary arterial blood compared to that of arterial blood: central venous ketone body ratio as a substitute for the arterial ketone body ratio.

To investigate the ketone body ratio (acetoacetate/3-hydroxybutyrate) of central venous blood compared to that of peripheral arterial blood, the acetoacetate and 3-hydroxybutyrate concentrations in paired peripheral arterial and central venous or pulmonary arterial blood were measured. The ketone body concentrations in superior and inferior vena cava blood were significantly (P < 0.0001) lower than those in peripheral arterial blood, whereas those in pulmonary arterial blood were almost the same as those in peripheral arterial blood. These results indicate that ketone bodies were metabolized in the muscles, which reduced their levels in vena cava blood, but ketone bodies newly produced by the liver were transported to the right side of the heart via the hepatic vein, giving concentrations in pulmonary arterial blood that were almost the same as those in peripheral arterial blood. On the other hand, the correlation coefficients (r2) of the arterial blood ketone body ratio to the ratio of superior and inferior vena cava and pulmonary arterial blood were 0.897, 0.767 and 0.882, respectively. The ratios of central venous ketone body ratio/arterial blood ketone body ratio were 0.89 +/- 0.15 in the superior vena cava, 0.64 +/- 0.18 in the inferior vena cava and 1.01 +/- 0.15 in the pulmonary artery.

Enzymatic method for determining ketone body ratio in arterial blood.

We have developed a new, sensitive, and rapid method for measuring the ketone body concentration in arterial blood and determining the arterial blood ketone body ratio. The procedure involves the sequential use of the enzymes 3-hydroxybutyrate dehydrogenase (3-HBDH; EC 1.1.1.30) and NADH oxidase, followed by a color-generating reaction with the hydrogen peroxide produced by the oxidase reaction. The amount of oxidized chromogen produced is proportional to the 3-hydroxybutyrate (3-HBA) concentration. The acetoacetate (AcAc) concentration is obtained after complete conversion of the AcAc to 3-HBA, in the presence of 3-HBDH. The total 3-HBA concentration is measured and then subtracted from the total ketone body concentration to give the AcAc concentration. This procedure may be applied to plasma samples and the absorbance change measured with an automated chemistry analyzer. Ketone body concentration may be determined over the range 0 to 400 mumol/L. The analysis takes approximately 12 min and requires only 30 microL of plasma.

High-performance liquid chromatography of arachidonic acid metabolites and its application to the determination of leukotriene B4 in stimulated leukocytes.

A highly sensitive high-performance liquid chromatography with fluorescence detection for the determination of arachidonic acid metabolites is described. The metabolites are converted into corresponding fluorescent derivatives by reaction with 3-bromomethyl-6,7-methylenedioxy-1-methyl-2(1H)-quinoxalinone in the presence of potassium hydrogen carbonate and 18-crown-6 in acetonitrile. The derivatives are separated on a reversed-phase column (Inertsil ODS) with aqueous acetonitrile and detected fluorimetrically. The detection limits are 5-15 fmol at a signal-to-noise ratio of 3 in a 10-microliter injection volume. The method is applied to the determination of leukotriene B4 produced in stimulated leukocytes.