5 p-CHOLESTANE · 3 a , 27-DIOL : NAD + OXIDOREDUCTASE AND 3 a-HYDROXY-5 p-CHOLESTAN-27-AL : NAD + OXIDOREDUCT ASE IN RAT LIVER EXTRACT * )
Using rat liver alcohol:NAD+ oxidoreductase and aldehyde:NAD+ oxidoreductase, the following facts were found: 1) 3a-hydroxy-5~-cholestan-27-al was reduced to 5fi -cholestane-3a, 27-diol by liver alcohol: NAD+ oxidoreductase. 2) The optimum pH was pH 7. 0 with potassium phosphate buffer and pH 8. 5 with Tris buffer. 3) The Km value of the substrate to the enzyme was 14. 3 μM. 4) 3a-Hydroxy5fi-cholestan-27al was oxidized to 3a-hydroxy5fi-cholestan27-oic acid by liver aldehyde: NAD+ oxidoreductase. 5) The optimum pH was pH 8. 5 with Tris buffer. 6) The Km value of the substrate to the enzyme was 26. 3 μM.
Horse liver 3 ,7 ,12 -trihydroxy-5 -cholestan-26-al dehydrogenase as a liver aldehyde dehydrogenase.
Abstract 3α,7α,12α-Trihydroxy-5β-cholestan-26-al dehydrogenase (3α,7α,12α-trihydroxy-5β-cholestan-26-al + NAD+ + H2O → 3α,7α,12α-trihydroxy-5β-cholestan-26-oic acid + NADH + H+) in a soluble fraction of horse liver was studied. 1. 1. Horse liver 3α,7α,12α-trihydroxy-5β-cholestan-26-al dehydrogenase consists of two components, the major one of which was purified about 70-fold by (NH4)2SO4 fractionation, gel filtration, ion-exchange column chromatography and hydroxylapatite column chromatography. 2. 2. 3α,7α,12α-trihydroxy-5β-cholestan-26-al dehydrogenase was always accompanied by liver aldehyde:NAD oxidoreductase (EC 1.2.1.3) activity, and the ratio of these two enzyme activities was not altered by purification. 3. 3. Both 3α,7α,12α-trihydroxy-5β-cholestan-26-al dehydrogenase and horse liver aldehyde:NAD+ oxidoreductase were reduced to a similar extent on inactivation of the purified enzyme by heating or by incubation with p-chloromercuribenzoate. 4. 4. The Km value for NAD+ of 3α,7α,12α-trihydroxy-5β-cholestan-26-al dehydrogenase was found to be roughly equal to that of liver aldehyde:NAD+ oxidoreductase. 5. 5. The possibility was discussed that both 3α,7α,12α-trihydroxy-5β-cholestan-26-al dehydrogenase and liver aldehyde:NAD+ oxidoreductase activities may be due to a single protein.
Pharmacokinetics of Mivacurium Isomers and Their Metabolites in Healthy Volunteers after Intravenous Bolus Administration
Background Previous studies report the pharmacokinetics of mivacurium isomers after an infusion using venous blood sampling. Although the extent of the mivacurium arterial‐venous gradient is not known, the sampling site is likely to influence mivacurium pharmacokinetic parameters because the drug is rapidly metabolized as it traverses the circulation. The objectives of this study were (1) to determine the pharmacokinetics of mivacurium isomers in healthy persons after intravenous bolus administration using intensive arterial blood sampling, and (2) to characterize the formation and elimination of mivacurium metabolites in human plasma. Methods Eight persons classified as American Society of Anesthesiologists physical status 1 or 2 who were scheduled to undergo elective surgery under balanced anesthesia received 0.15 mg/kg mivacurium chloride as an intravenous bolus. Arterial blood samples were collected every 10 s during the first 2 min and at frequent intervals for 4 h thereafter. Plasma concentrations of mivacurium isomers and their metabolites were determined by two stereoselective high‐performance liquid chromatographic methods coupled with fluorometric detection and noncompartmental pharmacokinetic parameters. Results Mean elimination half‐lives of the trans‐trans, cis‐trans, and cis‐cis isomers were 2.4, 2, and 28.5 min, respectively, with corresponding mean plasma clearances of 29.2, 45.7, and 6.7 ml [center dot] min‐1 [center dot] kg‐1. The volumes of distribution at steady state of the trans‐trans, cis‐trans, and cis‐cis isomers were 0.047, 0.054, and 0.189 l/kg, respectively. Plasma concentrations of monoester and alcohol metabolites peaked 25 s (median) after mivacurium injection, with half‐lives in the range of 90 min, except for the cis alcohol metabolite, which was only negligibly and transiently formed. Conclusions Substantial hydrolysis of mivacurium isomers by cholinesterases was confirmed by the rapid appearance of mivacurium metabolites in plasma. The intensive arterial sampling proved to be critical for the trans‐trans and cis‐trans isomers because the area under the curve between 0 and 2 min accounted for 75% and 86% of the total, respectively.