Corticosterone In Human Plasma Research Articles

Liquid chromatography and radioimmunoassay compared for determination of cortisol and corticosterone in plasma after a dexamethasone suppression test.

We developed sensitive, specific "high-performance" liquid chromatography (HPLC) for determining suppressed cortisol and corticosterone in human plasma and compared its efficacy with that of conventional radioimmunoassay (RIA) at concentrations in the nanogram per liter range. Steroids from a 0.5-mL aliquot of plasma were extracted by rapid-flow fractionation, with diethyl ether as mobile-phase solvent, diatomaceous earth granules as stationary-support material. Analytical recovery of the steroids approached 100%. Concentrations in plasma were determined from peak-height ratio calibration (dexamethasone internal standard). The analytical column contained silica gel and the solvent system was water/methanol/dichloromethane/n-hexane (0.1/3/30/66.9 by vol). We could measure the steroids before and 20 h after oral administration of 0.5 mg of dexamethasone. The detection limit was 300 ng per liter of plasma for corticosterone, 500 ng/L for cortisol, with CVs of less than 4%. Determining corticosterone after administration of dexamethasone, in four of 20 such samples we could determine concentrations greater than 300 ng/L; the others contained corticosterone between 100 and 300 ng/L, but these values could not be certified analytically. Mean concentrations of these hormones as determined by RIA substantially exceeded those by HPLC. Some cross reactions in RIA could not be considered negligible in spite of pre-column treatment of the extracts.

Radioassay of Cortisol and Corticosterone by a Modified Competitive Protein-Binding Method

A competitive protein-binding radioassay using adsorption was evaluated for the individual determination of cortisol and corticosterone. The competitive protein-binding assay using fuller's earth to separate bound and free cortisol was tested and found to offer no specificity for cortisol in favor of corticosterone. The introduction of a carbon tetrachloride/water partitioning procedure to separate corticosterone and cortisol made possible the individual determination of corticosterone and cortisol using the competitive protein-binding radioassay. The modified competitive protein-binding radioassay was evaluated as to precision, accuracy, and specificity; normal values of cortisol and corticosterone in human plasma were determined.

Simple method for the determination of plasma corticoids.

A simple dialysis method of estimating cortisol and corticosterone in human plasma has been described, utilizing the steroid-binding properties of plasma. The addition of increasing amounts of unlabeled cortisol to an equilibrium dialysis system containing standard plasma and a constant amount of cortisol-4-C14 caused a proportional decrease in the percentage of cortisol-4-C14 bound to the plasma protein. Preparations of plasma containing unknown amounts of cortisol also decreased binding; the cortisol content could thus be determined from a standard curve. This method required only one ml of test plasma and gave a standard deviation of ±1 μg over the range of 0–10 μg/100 ml. The technique was highly specific for cortisol and corticosterone in human plasma and was affected neither by hemolysis nor by drugs which interfered with other methods. Values obtained by this method were similar to those obtained using the method of Nelson and Samuels. The mean recovery of cortisol added to plasma was 91 %. Since m...

Influence of age on plasma adrenocorticosteroids in rats, rabbits, and guinea pigs

Circulating concentrations of free 17-hydroxycorticosteroids (17-OHCS) and "cortisol" and "corticosterone" were determined in rats, guinea pigs, and rabbits. (Quotation marks indicate that fluorescence present in plasma of these species has identical column chromatographic mobility of cortisol and corticosterone in human plasma.) In rats, "corticosterone" was present in greater amounts in adult than in young rats. Fluorescent material was also found in the "cortisol" fraction in both age groups but the 17-OHCS values were very low. In baby guinea pigs the fluorescent values for "cortisol" and "corticosterone" were about equal and were very high, as were the 17-OHCS values. During maturation all three values declined. In the younger age groups 17-OHCS values were two to three times greater than the "cortisol" values. In the two age groups of rabbits observed no 17-OHCS and only low "corticosterone" values were obtained. Instead, an unidentified, presumably steroidal, fluorescent material was found in the cortisol fraction.

Simultaneous determination of cortisol and corticosterone in human plasma by quantitative paper chromatography.

Summary and ConclusionsA method is presented for measuring Cortisol and corticosterone simultaneously in a single specimen of plasma. The steroids are purified by paper chromatography, eluted and measured by fluorometry. Losses incurred during analytical procedure are compensated by application of an isotope dilution correction. The normal range of corticosterone in human beings is 0 to 5 μtg/100 ml, with a mean of 1.3 ± 2.5 μg/100 ml. The normal range for Cortisol is 4.0 to 17.7 μg/100 ml, with a mean of 10.2 ± 3.6 μg/100 ml.

THE IDENTIFICATION OF CORTICOSTERONE IN HUMAN PLASMA AND ITS ASSAY BY ISOTOPE DILUTION

THE IDENTIFICATION OF CORTICOSTERONE IN HUMAN PLASMA AND ITS ASSAY BY ISOTOPE DILUTION