Bumetanide: radioimmunoassay and pharmacokinetic profile in humans

A simple, specific, and sensitive radioimmunoassay was developed for the determination of the diuretic bumetanide in plasma and urine. Antiserum to bumetanide was obtained from rabbits immunized with an immunogen prepared by covalently coupling the glycine conjugate of bumetanide to bovine serum albumin. Following extraction of the sample at pH 5.5 with ether, radioimmunoassay of the residue from the ether extract allows for the determination of bumetanide with a limit of sensitivity of about 1 ng/ml using 0.1 ml of plasma or urine. The specificity of the radioimmunoassay was established by comparison with specific radiometric and spectrofluorometric techniques. The pharmacokinetic profile of bumetanide in eight human subjects receiving single 2-mg oral doses of the drug was elucidated using the radioimmunoassay. The peak plasma levels ranged from 39 to 50 ng/ml at 1-4 hr after administration and declined with a mean apparent half-life of 1.17 hr. The mean plasma clearance rate was calculated to be 255 ml/min. During the first 24 hr, a mean of 43% of the bumetanide dose was excreted in the urine as intact drug.

[Peripheral arterial disease and diabetes mellitus(author's transl)]

Among a group of 286 patients with atherosclerotic arterial disease 35.3% had normal carbohydrate tolerance, 28% asymptomatic (biochemical or latent), and 36.7% overt diabetes mellitus. There was a tendency towards peripheral artery involvement and a greater incidence of coronary heart disease (myocardial infarction, changes in ST-T segment) among patients with asymptomatic or overt diabetes, figures being comparable for men and women. Most of the patients with atherosclerotic arterial disease without diabetes mellitus were in stage II, while in diabetics there was a shift towards stages I and IV. There was no significant correlation between incidence, symptoms, and location of atherosclerotic arterial disease, on the one hand, and duration of overt diabetes, on the other.

The role of a 5alpha-hydroxylated intermediate in the formation of the 5, 6-double bond in cholesterol biosynthesis

If the biological conversion of cholest-7-en-3beta-ol (I) into cholesterol (IV) occurred thorugh the intermediacy of cholest-7-ene-3beta,5alpha-diol (II) then the factor(s) adversely affecting the convwesion of the 5alpha-hydroxy sterol (II) into cholesterol must at least equally adversely affect the formation of cholesterol from cholest-7-en-3beta-ol. By using partial denaturation techniquws and dual-labelled precursors it was shown that the enzyme system responsible for the conversion of the 5alpha-hydroxy sterol (II) into cholesterol denatured faster than that for the corresponding conversion from cholest-7-en-3beta-ol (I).