Determination of a renin inhibitor in plasma by solid-phase extraction using acetone as protein binding displacer followed by on-line high-performance liquid chromatography.
H 218/54 is a potent inhibitor of human renin activity (pIC50 = 8.3 at pH 6) and is therefore a potential agent for blood pressure reduction. This lipophilic compound is highly bound to plasma proteins, e.g. 99.7% in rats and 99.6% in humans. For pharmacokinetic studies, a quantitative assay for 3H-H 218/54 in plasma has been developed. On top of an AASP phenyl solid-phase cartridge 70 microliters of rat plasma or 1 ml of cynomolgus plasma was mixed with 200 microliters of water containing 20% acetone. The acetone displaced the substance from plasma proteins without precipitation of the sample and clogging of the extraction column. The mixture was passed through the cartridge, which adsorbed 3H-H 218/54. The cartridge was placed in an AASP autosampler connected to a reversed-phase LC system, with a Vydac C-18 column and CH3CN-H2O-TFA (60:40:0.1, v/v/v) as mobile phase. The effluent from the separation column was collected in fractions for radioactivity counting. Recovery, as measured after adding various amounts of tritium-labelled H 218/54 to blank plasma followed by repeated analysis of the samples, was close to 100% with relative standard deviations between 1.4 and 3.0%. At the lowest level tested, 200 dpm per sample, the recovery was 120% with a relative standard deviation of only 10%. The sensitivity of the method will depend on the specific radioactivity of the dose given.
Renberg
L
L
Pharmacokinetics and Drug Metabolism, Astra Hässle AB, Mölndal, Sweden.
Hoffmann
K J
KJ
D000096:Acetone / Q000737:chemistry; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003510:Cyclohexanes / Q000097:blood*; D006801:Humans; D008252:Macaca fascicularis; D010865:Pilot Projects; D011485:Protein Binding; D011863:Radioimmunoassay; D051381:Rats; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014633:Valine / Q000031:analogs & derivatives* / Q000097:blood; D000092502:Renin Inhibitors
D000096:Acetone; D003510:Cyclohexanes; D014633:Valine; D000092502:Renin Inhibitors; C080611:H 218-54