Improved high-performance liquid chromatographic method for analysis of cyclosporin A using an automated sample processor

Simple determination of cyclosporine in human whole blood by high-performance liquid chromatography

A simple and reproducible high-performance liquid chromatography (HPLC) method was developed for determination of cyclosporine (CyA, also known as cyclosporin A) in human whole blood. The method entailed direct injection of the blood samples after deproteination using acetonitrile. Chromatography was carried out using an ODS column under isocratic elution with acetonitrile-5mM disodium hydrogen phosphate (75:25, v/v), pH 5.1 at 70 degrees C and a detector set at 210 nm. The mean absolute recovery of cyclosporine from blood was 97%, and the linearity was assessed in the range of 100-3000 ng/ml blood, with a correlation coefficient of greater than 0.999. The limit of quantification and detection of the present method were 100 and 50 ng/ml, respectively. This method has been used to analyze several hundred human blood samples for bioavailability studies.

Before the injection--modern methods of sample preparation for separation techniques

The importance of sample preparation methods as the first stage in an analytical procedure is emphasised and examined. Examples are given of the extraction and concentration of analytes from solid, liquid and gas phase matrices, including solvent phase extractions, such as supercritical fluids and superheated water extraction, solid-phase extraction and solid-phase microextraction, headspace analysis and vapour trapping. The potential role of selective extraction methods, including molecular imprinted phases and affinity columns, are considered. For problem samples alternative approaches, such as derivatisation are discussed, and potential new approaches minimising sample preparation are noted.

Blood pressure and endocrine responses to changes in dietary sodium intake in cardiac transplant recipients. Implications for the control of sodium balance

BACKGROUND

The role of cardiac extrinsic innervation in the regulation of sodium balance and blood pressure is controversial.

METHODS AND RESULTS

We performed a double-blind study of endocrine and blood pressure responses to 5 days of low- (LS, 10 mmol/d) and 5 days of high- (350 mmol/d) sodium intake in 12 cardiac transplant recipients, 12 matched healthy subjects, and 12 matched subjects with untreated essential hypertension. In transplant recipients on low sodium, supine blood pressure was 137/94 +/- 8/4 (mean +/- SEM) mm Hg and plasma atrial natriuretic peptide (ANP) was 59.3 +/- 6.3 pg/mL; on high sodium, blood pressure was 148/97 +/- 5/3 mmHg (P < .05 for systolic pressure versus LS), and ANP was 94.3 +/- 10.6 pg/mL (P < .01 versus LS), respectively. Plasma ANP for those on each diet was significantly higher in the cardiac transplant recipients than in healthy or hypertensive controls; relative changes in plasma ANP in changing from low- to high-sodium diet were similar in each group. Urinary sodium excretion by the fifth day of each diet was similar in each group. Suppression of plasma renin activity and aldosterone by high-sodium diet was blunted in cardiac transplant recipients compared with healthy subjects (respectively, plasma renin activity: 1.41 +/- 0.30 versus 0.68 +/- 0.21 ng.mL-1 x h-1, P < .05; aldosterone: 391 +/- 35 versus 166 +/- 21 pmol/L, P < .05).

CONCLUSIONS

These results suggest that extensive denervation of the heart does not result in major abnormalities in regulation of large changes in sodium intake and that intact cardiac innervation is not required for plasma ANP responses to altered sodium intake. Blood pressure after cardiac transplantation is sensitive to reduced sodium intake.

New fluorescent derivatives of cyclosporin for use in immunoassays

The synthesis of new fluorescent derivatives of cyclosporin is described and their affinity with the specific Sandoz monoclonal antibody investigated. Synthesis was carried out using cyclosporin-C-hemisuccinate as the starting material with monodansylcadaverine, 4-bromomethyl-7-methoxycoumarin, and 4-bromomethyl-6,7-dimethoxycoumarin as labels. After extraction the derivatives were purified by HPLC and their binding affinity with the monoclonal antibody evaluated by the Incstar Cyclo-Trac SP radioimmunoassay. All three derivatives showed good binding and it is suggested that they may be of use in an immunoassay for measuring cyclosporin.