Kunio Kihara

Determination of creatinine with a sensor based on immobilized glutamate dehydrogenase and creatinine deiminase

Abstract Glutamate dehydrogenase and creatinine deiminase are immobilized by adsorption on wet poly(vinyl chloride) membranes. Creatinine is determined by a sensor consisting of the two membranes placed over an ammonia-sensing electrode. Endogenous ammonia is removed as it passes through the glutamate dehydrogenase layer. Creatinine (1–50 mg dl −1 ) is converted to ammonia in the inner creatinine deiminase layer and is detected by the ammonia electrode. The assay requires 3 min, the minimum detectable concentration is 1 mg dl −1 at pH 8.5, and the precision is ca. 5%. Endogenous ammonia can be tolerated up to 2 × 10 −4 M.

Determination of glutamate-pyruvate transaminase activity in blood serum with a pyruvate oxidase/poly(vinyl chloride) membrane sensor

Abstract Pyruvate oxidase (E.C. 1.2.3.3.) is immobilized by adsorption on a wet PVC membrane. Glutamate-pyruvate transaminase activity (5–1600 IU l −1 ) in serum is determined by a pyruvate oxidase sensor consisting of the immobilized pyruvate oxidase coupled to a platinum electrode for measuring hydrogen peroxide, after an l -alanine—α-ketoglutarate reaction. The assay requires ⩽60 s, and has a precision of 2–3%. Endogenous pyruvate should not interfere if measurements are made > 30 s after starting the reaction.

The bile acid binding and hypocholesterolemic activity of anion—exchange resins bearing the imidazolium salt group

Abstract A new anion—exchange resin bearing imidazolium pendant groups on a polystyrene copolymer skeleton was synthesized. This resin is a white odorless powder and the bile acid binding activities in vitro were much more potent than those of cholestyramine. The ion- exchange equilibrium coefficient K phosphoric acid ion − bile acid ion − was 271, compared to that of cholestyramine which was 32. The hypocholesterolemic activity of this resin in cholesterol-fed rabbits proved to be 1.5-fold more potent than that of cholestyramine. Thus, the effective reduction of plasma cholesterol may be achieved with significantly lower doses of this resin.