Biomedical subjects
Publications and source records attributed to B A Persson.
Possible arrhythmogenic side-effects of the positive inotropic agent prenalterol were studied in conscious dogs, three to four days after coronary artery ligation. Prenalterol showed a propensity to cause arrhythmias in one out of eight dogs, thereby confirming published data from clinical studies.
Liquid chromatography with electrochemical detection is used for the determination of adrenaline, noradrenaline and dopamine in rat heart tissue, and the method has also been applied to the determination of basic levels of these compounds in blood plasma. The catecholamines are isolated from the biological sample by adsorption onto alumina and are then desorbed by elution with perchloric acid. The stability of the compounds during the different stages in the work-up process has been studied. A greatly simplified procedure for the preparation of alumina is presented. Both ion-pair reversed-phase and ion-exchange liquid chromatography have been used for the separation of the catecholamines. For plasma samples the method has been validated against radioenzymatic assay and the choice of method is discussed.
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Apomorphine is extracted from plasma or tissue homogenate with ethyl acetate. After back-extraction into hydrochloric acid, the apomorphine is extracted as an ion pair with 3,5-di-tert.-butyl-2-hydroxybenzene sulphonate into a small volume of methylene chloride and the solution is injected into the chromatographic column. Apomorphine is separated on microporous silica with a mixture of aqueous perchloric acid, methanol and methylene chloride as the mobile phase. With absorbance measurement of the eluent at 254 nm the method permits the determination of 15 pmol of apomorphine in 1 ml of plasma or in a rat brain. The coefficient of variation was 4% at the 100 pmol level.
1. The plasma levels and the urinary excretion of hydrochlorothiazide (HCT) have been studied after administration of single doses of 12.5 and 25 mg of the drug in solution and in combination with 100 mg of the selective beta 1-adrenoreceptor antagonist metoprolol in a rapidly dissolving tablet. 2. Metoprolol did not significantly influence the bioavailability or the time-course of HCT. 3. HCT had no significant effect on the time-course or the plasma levels of metoprolol. The average half-life, 4.4 +/- 0.9 h, is about the same as previously observed for separate doses of this drug. 4. It seems unlikely that repeated doses of the combination product studied will lead to biopharmaceutic or pharmacokinetic interactions of clinical importance.
High-performance liquid chromatography has been employed in the development of assay methods for six antiarrhythmic drugs, disopyramide, lidocain, tocainide, procainamide, aprinidine and quinidine. Liquid-solid chromatography has been used and separation times of about 5 min have usually been sufficient. Owing to the capacity of the liquid chromatographic system, sample preparation has been minimized to a single extraction and direct injection of a considerable part of the extract. The overall time of analysis is very short and the methods are well suited for monitoring of plasma levels of the antirrhythmic drugs and in some instances (procainamide and disopyramide) also for their main metabolites. UV detection at the optimal wavelength has permitted determinations down to 50 pmole (20 ng) in 1 ml of plasma for the amines with high absorbance.
A selective analytical method for the determination of methylguanidine in plasma in biological fluids has been developed. Methylguanidine is extracted in a column to dichloromethane as an ion pair with hexanitrodiphenylamine (dipicrylamine). It is isolated from coextracted compounds by partition chromatography as the picrate ion-pair. The methylguanidine fraction is collected and after reextraction to a buffer solution the methylguanidine content is quantitatively determined photometrically as picrate. An absolute recovery of 95 +/- 5% was obtained in the concentration range 1.5-10 microgram/ml plasma. The concentration of methylguanidine in plasma was higher in uremic patients, (44.4 +/- 5.71 mumol/l in conservatively-treated and 42.4 +/- 7.87 mumol/l in dialysis-treated patients) than in normal subjects, (4.0 mumol/l), but still lower than reported by other investigators using non-specific methods and also lower than the concentrations found to be toxic in experimental animals. There was a significant correlation between methylguanidine and creatinine concentration but no correlation between methylguanidine and urea concentration in plasma. No obvious relation was found between plasma methylguanidine concentration and various uremic symptoms, mode of treatment or protein intake.
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Liquid-liquid chromatography based on the ion-pair partition technique gives separation systems of high efficiency when silica micro-particles are used as the support for the stationary phase. With 10-mum particles, plate heights of the order of 40-70 mum have been achieved with a linear velocity of 0.25 cm/sec. The retention in ion-pair partition systems is determined by the nature and concentration of the counter ion, and the properties of the mobile phase also have a major influence. It is often possible to predict the selectivity, and this can be controlled by varying the composition of the mobile phase. This paper describes the application of ion-pair partition chromatography to the bioanalysis of drugs, drug metabolites and biogenic substances. Typical counter ions in the stationary phase were methanesulphonate and perchlorate for ammonium compounds and tetrabutylammonium for the separation of organic anions. Determinations by liquid chromatography were demonstrated for quinidine and dihydroquinidine, metanephrine and normetanephrine and for imipramine and its demethyl metabolite in plasma. A quaternary ammonium compound, QX-572, was determined in urine and chromatograms are shown for the isolation of indoleacetic and hydroxyindoleacetic acid in urine. The methods have been used in routine analysis. Ultraviolet detection has permitted the determination of highly absorbing compounds down to the 10-ng level in plasma and urine.
A method for determination of acetylcholine in small, discrete biological objects by use of ion-pair technique has been developed. Acetylcholine is extracted as an ion pair with 3,5-di-t-butyl-2-hydroxybenzenesulphonate and separated from co-extracted components by ion-pair partition chromatography with picrate as the counter ion and porous cellulose as support. The quantitative evaluation is made from the acetylcholine peak in the chromatogram obtained by ultraviolet detection. Acetylcholine has been analysed in 1 cm large pieces of rat sciatic nerve containing about 60 pmol (10 ng). The overall recovery of the method is 100 +/- 10% at the 120 pmol level of acetylcholine in a sample.
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