Fatal strychnine poisoning: application of gas chromatography and tandem mass spectrometry

The history and toxicological findings in a case of suicidal fatal strychnine poisoning are presented along with a description of the analytical methods. Detection and quantitation of strychnine in body fluids and tissues was performed by gas chromatography (GC) with nitrogen-phosphorus detection, using organic extraction and calibration by a standard addition method. Strychnine concentrations in subclavian blood (1.82 mg/mL), inferior vena cava blood (3.32 mg/mL), urine (3.35 mg/mL), bile (11.4 mg/mL), liver (98.6 mg/kg), lung (12.3 mg/kg), spleen (11.8 mg/kg), brain (2.42 mg/kg), and skeletal muscle (2.32 mg/kg) were determined. Confirmation of strychnine in blood and tissue was performed by GC with detection by tandem ion-trap mass spectrometry (MS). GC-MS-MS analysis, employing electron ionization followed by unit mass resolution and collision-induced dissociation of strychnine, resulted in confirmatory ions with mass-to-charge ratios of 334 (parent ion), 319, 306, 277, 261, 246, 233, and 220. Additional confirmation was provided by GC-MS-MS-MS analysis of each confirmatory ion, revealing an ion fragmentation pathway consistent with the molecular structure of strychnine. The case demonstrates body tissue and fluid distribution of strychnine in a fatal poisoning and the application of tandem MS in medical examiner casework.

Urinary free deoxypyridinoline by chemiluminescence immunoassay: analytical and clinical evaluation

We evaluated an automated chemiluminescence immunoassay (CLIA) developed for the measurement of urinary free deoxypyridinoline (DPD). The new DPD method by CLIA is based on the competition of DPD with particle-bound pyridinoline for a limited amount of monoclonal mouse anti-DPD antibody. Total imprecision (CV) was 3.2-9.0% at 30-270 nmol/L. Regression analysis of urinary DPD concentration (second morning-void) measured by CLIA (y) and enzyme immunoassay (EIA) for adult volunteers (n = 449) with and without bone disease revealed a best fit equation of: y = 1.08 +/- 0.03x - 1.15 +/- 0.98 nmol/L (r = 0.964, S(y/x) = 14 nmol/L). CLIA and EIA methods were correlated with HPLC measurement of urinary free DPD (r = 0.846 and 0.871, respectively). For healthy adults, the creatinine-normalized excretion of DPD (mean +/- SD) measured by CLIA for 61 men (4.1 +/- 1.2 micromol DPD/mol creatinine) and 76 premenopausal women (5.3 +/- 1.8 micromol DPD/mol creatinine) did not differ significantly (P >0.05) from DPD excretion measured by EIA, and both immunoassays showed a significant gender difference (P <0.001) in reference intervals. In a clinical trial, DPD excretion (micromol DPD/mol creatinine) measured by CLIA differed substantially from the reference population for 54 untreated pagetic (12.7 +/- 8.0 SD), 255 untreated osteoporotic (7.5 +/- 4.1), 21 osteomalacic (12.4 +/- 8.5), 17 primary hyperparathyroid (9.4 +/- 4.4), and 14 secondary hyperparathyroid (9.2 +/- 5.1) patients. Clinical sensitivities of the CLIA and EIA methods range from 38% to 80% in bone disorders and limit the use of the DPD measurement in disease detection. DPD excretion after pamidronate treatment in a subgroup of the pagetic patients fell dramatically as assessed by CLIA or EIA. We conclude that the automated CLIA method for DPD is a convenient and reliable method that may aid in the evaluation and management of bone disease and is applicable to high volume testing in the routine clinical laboratory.

Comparative pharmacokinetics and renal effects of cyclosporin A and cyclosporin G in renal allograft recipients

Cyclosporin G (CSG) has produced less nephrotoxicity than cyclosporin A (CSA) at equivalent doses in animal models. Conflicting results have been reported concerning differences in the pharmacokinetics of CSA and CSG in preclinical studies, and no data exist regarding the effect of steady-state oral administration of CSG on renal function in transplant patients or CSG-induced release of endothelin and nitric oxide (NO) in vivo. The objective of the study was to examine steady-state pharmacokinetic profiles of adult renal allograft recipients receiving CSA and CSG in relation to concentrations of endothelin-1 and NO2/NO3 in urine and plasma, creatinine clearance (Clcr), and urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG) 9 months after transplantation. Concentrations of CSA and CSG were measured in whole blood over a 12-hour dose interval by both a monoclonal and polyclonal fluorescence polarization radioimmunoassay for CSA. A metabolite fraction was defined as the numerical difference between the levels obtained at each time point by both assays. Patient groups were defined as follows: group 1: initial CSA (n = 6); group 2: initial CSG (n = 7); group 3: five of the seven patients in group 2 taking CSG subsequently undergoing conversion to CSA; group 4: the same five patients in group 3 restudied 1 month after 1:1 dosage conversion to CSA; and group 5: CSA groups 1 and 4 combined (n = 11). In group 1, the metabolite fraction accounted for 32% to 54% of the total measurable drug concentration at each time point, whereas in group 2, the metabolite fraction accounted for at most 10% to 15% of the total drug levels measurable by polyclonal fluorescence polarization radioimmunoassay. Although there were no significant differences in any of the mean pharmacokinetic parameters between groups using monoclonal fluorescence polarization radioimmunoassay, the normalized area under the concentration-time curve (NAUC) value was less in four of five patients after conversion from CSG to CSA, with a more variable and delayed time to reach peak concentration (tmax) but equivalent apparent oral clearance (Clpa) values. Clcr was found to change significantly with time in groups 1 and 5 but not in group 2, with CSA producing a more profound and sustained decrease than CSG. Endothelin-1 and NO2/NO3 levels in plasma and urine remained relatively constant after administration of both CSA and CSG, and there were no significant differences between groups 3 and 4 regarding mean endothelin-1 and NO2/NO3 concentrations in plasma, urinary release of endothelin-1 and NO2/NO3, and mean AUC of endothelin-1 and AUC of NO2/NO3. However, monoclonal NAUC correlated significantly with total urinary endothelin-1 within CSA groups 1 and 5 but not within CSG group 2. Metabolite NAUC correlated significantly with total urinary NAG within CSA group 1. Although limited by the small number of patients, this study suggests that 1) CSG may produce less of a reduction in Clcr over time after oral administration at steady state than does CSA, and 2) this beneficial effect of CSG may be in part due to decreased intrarenal release of endothelin-1, as urinary excretion of endothelin-1 seemed to correlate better with CSA than with CSG exposure.

Metabolism of serotonin to N-acetylserotonin, melatonin, and 5-methoxytryptamine in hamster skin culture

Biotransformation of [3H]serotonin by cultured hamster skin to 3H-metabolites corresponding to N-acetylserotonin (NAS), melatonin, and 5-methoxytryptamine (5-MT) was demonstrated. This process was time-dependent, with the highest production of radioactive NAS and melatonin metabolites after 3 and 5 h of incubation followed by a decrease in the rate of metabolite release into the media. Conversely, the formation of radioactive metabolite corresponding to 5-MT increased gradually during skin culture, reaching the highest level after 24 h of incubation. The production of 3H-metabolites, corresponding to NAS, melatonin, and 5-MT, was stimulated by forskolin with a maximum effect of forskolin at 10 microM concentration. The gas chromatographic/mass spectroscopy analysis of the fraction eluting at the retention time of NAS standard material showed that it contained NAS, further confirming production and release of NAS into the media by hamster skin. Therefore, we conclude that mammalian skin can acetylate serotonin to NAS and postulate that the NAS is further metabolized by the skin to form melatonin which is subsequently transformed to 5-MT.

Fucosyltransferase and alpha-L-fucosidase activities and fucose levels in normal and malignant endometrial tissue

Previous immuno- and lectin-histochemical studies using mAbs and Ulex europaeus lectin I, which recognize various fucose-containing blood group antigens, have shown an increased expression of Lewis and H blood group antigens in endometrial carcinoma. We investigated the biochemical basis of aberrant fucose-containing antigen expression by comparing the activity of fucosyltransferases (FTase) and alpha-L-fucosidase in tissue biopsies from normal (n = 18) and malignant (n = 20) endometrium. Alteration of FTase activity in tumor tissue homogenates was evaluated by using a panel of FTase substrates including N-acetyllactosamine (type 2), lacto-N-biose I (type 1), and phenyl-beta-D-galactoside. Based on histological subtyping, the endometrioid group (n = 14) showed a significant (P < 0.05) increase in tumor FTase activity with all three substrates, while no significant increase was detected for the papillary serous group (n = 4). Matched pair analysis of normal and tumor tissue from a subgroup (n = 5) of the patients with increased tumor enzyme activity also showed higher FTase activity (P < 0.05) in the tumor tissue when the type 1 substrate was used. Regression analysis showed a correlation between the FTase activities acting on type 2 or type 1 substrates (r = 0.821 and r = 0.722, respectively) and the endogenous fucose levels in tumor homogenates. Spectrophotometric analysis of alpha-L-fucosidase activity using p-nitrophenyl-alpha-L-fucoside revealed a higher activity in tumor homogenates than in normal homogenates (P < 0.05) and, therefore, could not account for the enhanced expression of fucose-containing antigens. The current study suggests that aberrant expression of fucose-containing antigens, such as the H and the Lewis blood-group antigens, in endometrial carcinoma is consequential to the change in FTase rather than in alpha-L-fucosidase activity. In addition, the investigation suggests that different glycosylation mechanisms are operative in different subtypes of endometrial cancer.

Clinical and analytical evaluation of an immunoradiometric assay for corticotropin

We evaluated a new IRMA developed commercially for the measurement of corticotropin (ACTH) in human plasma. The assay involves purified polyclonal goat capture antibodies specific for ACTH 26-39 and an 125I-labeled monoclonal signal antibody specific for ACTH 1-17. CVs for intraassay and total precision at ACTH concentrations between 9 and 801 ng/L ranged from 2.5% to 4.7% and from 3.3% to 9.3%, respectively, with an assay detection limit of 1.7 ng/L. The reference interval determined for adults with the new method (16-52 ng/L) differed significantly (P < 0.05) from that for an established ACTH IRMA (9-54 ng/L). Method comparison with clinical samples (n = 179) revealed a correlation coefficient of 0.970 and a best-fit equation of y (new IRMA) = (1.011 +/- 0.019)x + (4.17 +/- 3.31) with Sylx = 40.2. Both methods showed equivalent clinical sensitivity in evaluating Cushing disease, adrenal tumors, ectopic ACTH-producing tumors, hypopituitarism, steroid suppression, surgical adrenalectomy, Nelson syndrome, Addison disease, and corticotropin-releasing hormone stimulation. We conclude that the new IRMA is technically simple to perform and provides a specific and sensitive method for evaluating of adrenocortical function.

Clinical and analytical evaluation of an immunoradiometric assay for corticotropin

We evaluated a new IRMA developed commercially for the measurement of corticotropin (ACTH) in human plasma. The assay involves purified polyclonal goat capture antibodies specific for ACTH 26-39 and an 125I-labeled monoclonal signal antibody specific for ACTH 1-17. CVs for intraassay and total precision at ACTH concentrations between 9 and 801 ng/L ranged from 2.5% to 4.7% and from 3.3% to 9.3%, respectively, with an assay detection limit of 1.7 ng/L. The reference interval determined for adults with the new method (16-52 ng/L) differed significantly (P &lt; 0.05) from that for an established ACTH IRMA (9-54 ng/L). Method comparison with clinical samples (n = 179) revealed a correlation coefficient of 0.970 and a best-fit equation of y (new IRMA) = (1.011 +/- 0.019)x + (4.17 +/- 3.31) with Sylx = 40.2. Both methods showed equivalent clinical sensitivity in evaluating Cushing disease, adrenal tumors, ectopic ACTH-producing tumors, hypopituitarism, steroid suppression, surgical adrenalectomy, Nelson syndrome, Addison disease, and corticotropin-releasing hormone stimulation. We conclude that the new IRMA is technically simple to perform and provides a specific and sensitive method for evaluating of adrenocortical function.

Inhibition of calcineurin phosphatase activity in adult bone marrow transplant patients treated with cyclosporine A

In vitro studies have demonstrated that cyclosporine A (CsA) acts by inhibiting the phosphatase activity of calcineurin, an important mediator of T-cell activation. The relationship of CsA administration in vivo, calcineurin activity, and graft-versus-host disease (GVHD) has yet to be studied. The calcineurin activities of mononuclear cells isolated from 62 bone marrow transplant recipients and 12 normal volunteers were determined and analyzed with respect to administration of CsA, presence or absence of CsA in plasma, and presence or absence of GVHD. Of 62 patients, 33 were taking CsA and 29 were not. Early posttransplant (< 100 days), the calcineurin activity of patients on CsA was significantly lower than that of patients not on CsA (P = .0004) and than that of normal volunteers (P < .0001). Similarly, late posttransplant (> 100 days), the calcineurin activity of patients taking CsA was inhibited compared with normal volunteers (P < .05). The calcineurin activity of patients with acute GVHD who were taking CsA was lower than that of patients on CsA without acute GVHD matched for time posttransplant (P = .02). Calcineurin activity in patients on CsA with chronic GVHD was similar to those without chronic GVHD on drug. In conclusion, calcineurin activity is significantly suppressed by in vivo administration of CsA. The lower calcineurin activity of patients on CsA with acute GVHD suggests that CsA-resistant GVHD is not the result of inadequate suppression of calcineurin activity. These data suggest that if inhibition of calcineurin is the only physiologic target of CsA administration, simply increasing doses of CsA or treatment with other inhibitors of calcineurin, such as FK506, would not be expected to ameliorate GVHD.

Benztropine identification and quantitation in a suicidal overdose

For a human fatality involving suspected overdose with the anticholinergic agent benztropine, GC-MS analysis was utilized for identification, quantitation, and investigation of metabolism. Organic extracts of blood and urine were analyzed by a capillary-column gas chromatograph interfaced with an ion-trap mass spectrometer, which was programmed for wide-spectrum data acquisition. Electron impact and chemical ionization were used for benztropine detection. The chemical structures of the ion fragments are proposed. Benztropine-d3 was synthesized and used as an internal standard. Quantitative determinations of benztropine revealed 0.183 mg/L in blood and 7.12 mg/L in urine from the decedent. Drug concentrations were interpreted relative to the case findings, published data, and a limited evaluation of the therapeutic concentrations in psychiatric patients. In addition, the possible metabolic conversion to norbenztropine was investigated by the synthesis of the norbenztropine derivative. Chromatographic evaluation of samples from the case study did not reveal significant bioconversion via the N-desmethylation pathway.

Comparative quantitative immunohistochemical and immunoradiometric determinations of cathepsin D in endometrial adenocarcinoma: predictors of tumor aggressiveness

Previous comparisons of results of biochemical and immunohistochemical assays for Cathepsin D protease (CD) have conflicted in breast tumors and have not been applied to endometrial adenocarcinomas. We studied CD levels in 31 endometrial adenocarcinomas comparing immunoradiometric assay (IRA) of tumor cytosol with quantitative immunohistochemistry (QIH). Corresponding formalin-fixed paraffin-embedded sections were stained with a polyclonal antibody and measured with the CAS 200 Image Analyzer using a modified cytoplasmic antigen quantification program. Significant and trended increases in CD levels by IRA and QIH were similarly seen in high-grade tumors (IRA p < 0.001; QIH p < ns), papillary serous carcinoma subtype, and cases with deep myometrial invasion (IRA p < 0.005; QIH p < 0.04). Higher mean CD levels by QIH correlated significantly with positive lymph node status (LN+ 0.18 U/cell; LN- 0.09 U/cell; p < 0.03). No correlation of CD by IRA or QIH with estrogen- and progesterone-receptor tumor status was seen. We conclude that image quantification immunohistochemistry is an objective and sensitive method for determining tumor CD levels, CD by QIH directly correlates with standard prognostic indicators such as myometrial invasion and lymph node metastasis, and CD by QIH may prove clinically useful as a predictive adjuvant study for endometrial adenocarcinoma biopsy specimens.

Preparative chromatographic purification of cyclosporine metabolites

Polar and primary metabolites of cyclosporin A (CsA) have successfully been isolated by a novel separation protocol. An efficient, easy-to-scale-up chromatographic adsorption/desorption operation recovers polar and primary CsA metabolite pools from large volumes of urine; purified CsA metabolites are subsequently obtained by high-resolution preparative elution chromatography of the semipurified metabolite pools. Separations performed on a semipreparative scale [with a 250 x 9.4 mm (i.d.) reversed-phase HPLC column] yielded microgram quantities of CsA metabolites at &gt; 97% purity, as determined by fast atom bombardment mass spectrometry. These separations also yielded two previously unreported CsA metabolites, similar to AM1A but with an additional hydroxylation. The yield of metabolites was increased to several milligrams by performing the separations with a preparative-scale [250 x 21.2 mm (i.d.)] reversed-phase column. The production rate of purified primary CsA metabolites was greatly increased by performing the separation with the preparative-scale column under conditions of severe mass overloading. In a single chromatographic run, we successfully isolated 11.0 and 5.0 mg of AM1 and AM1c, respectively, at a purity of &gt; 97%. As expected, this increase in the yield of purified metabolites was accompanied by a decrease in the overall recovery. This separation scheme enables the rapid processing of large volumes of urine for isolation of the milligram quantities of CsA metabolites necessary to assess their biological activity. The procedure is applicable to small- or large-scale metabolite isolation and provides a ready source of purified metabolites for in vitro and whole-animal studies.

Preparative chromatographic purification of cyclosporine metabolites

Polar and primary metabolites of cyclosporin A (CsA) have successfully been isolated by a novel separation protocol. An efficient, easy-to-scale-up chromatographic adsorption/desorption operation recovers polar and primary CsA metabolite pools from large volumes of urine; purified CsA metabolites are subsequently obtained by high-resolution preparative elution chromatography of the semipurified metabolite pools. Separations performed on a semipreparative scale [with a 250 x 9.4 mm (i.d.) reversed-phase HPLC column] yielded microgram quantities of CsA metabolites at > 97% purity, as determined by fast atom bombardment mass spectrometry. These separations also yielded two previously unreported CsA metabolites, similar to AM1A but with an additional hydroxylation. The yield of metabolites was increased to several milligrams by performing the separations with a preparative-scale [250 x 21.2 mm (i.d.)] reversed-phase column. The production rate of purified primary CsA metabolites was greatly increased by performing the separation with the preparative-scale column under conditions of severe mass overloading. In a single chromatographic run, we successfully isolated 11.0 and 5.0 mg of AM1 and AM1c, respectively, at a purity of > 97%. As expected, this increase in the yield of purified metabolites was accompanied by a decrease in the overall recovery. This separation scheme enables the rapid processing of large volumes of urine for isolation of the milligram quantities of CsA metabolites necessary to assess their biological activity. The procedure is applicable to small- or large-scale metabolite isolation and provides a ready source of purified metabolites for in vitro and whole-animal studies.

Correlation of tumor cytosol cathepsin D with differentiation and invasiveness of endometrial adenocarcinoma

The lysosomal acidic protease cathepsin D, a recognized independent predictor of prognosis in human breast cancer, has not been studied widely in patients with endometrial adenocarcinoma. Cathepsin D levels (52-kD precursor plus 48-kD intermediate and 34/14-kD mature form) were measured in tumor cytosols from 26 hysterectomy specimens by immunoradiometric assay. Significant correlation between cathepsin D levels and tumor differentiation was noted with linear increase in cathepsin D from 8 pmol/mg (standard error of the mean [SEM], 1.73 pmol/mg) for Grade I tumors to 28 pmol/mg (SEM, 3.91 pmol/mg) for Grade III tumors. A group of four papillary serous carcinomas showed relatively high cathepsin D levels reaching 39 pmol/mg. A significant stepwise increase in cathepsin D levels was associated with increased depth of myometrial invasion. Noninvasive tumors averaged 7 pmol/mg (SEM, 4.0 pmol/mg); intramural tumors averaged 15 pmol/mg (SEM, 2.45 pmol/mg); and transmural invasive tumors averaged 30 pmol/mg (SEM, 3.72 pmol/mg). There was no significant correlation of cathepsin D levels with age, estrogen/progesterone receptor hormone status, clinical stage, and lymph node metastasis. Cathepsin D levels correlate significantly with tumor differentiation and myometrial invasiveness and may show promise as a clinically useful adjunct to prognosis assessment and the planning of therapy for patients with endometrial adenocarcinoma.

Assessment of the in vivo immunosuppressive activity of the major cyclosporine metabolite by leukemia allograft rejection

AM1 (M17) is the major metabolite of cyclosporine found in the blood of human transplant recipients, and trough levels of this derivative exceed those of the parent compound approximately two-fold. Studies performed in vitro indicate that AM1 retains only 10-20% of the biological activity of the parent compound, but very little is known about its in vivo immunosuppressive effects. We therefore developed a rapid and sensitive method, based on the rejection of allogeneic L1210 (H-2d) leukemia cells by C57BL/6 (H-2b) mice, to assess the immunosuppressive activity of AM1 in vivo. Rejection of the leukemia allograft was determined by analyzing the spleens from mice injected intravenously with 10(5) L1210 cells for the presence of H-2Kd-positive cells by flow cytometry using an FITC-conjugated monoclonal anti-H-2Kd antibody. Nonimmunosuppressed mice rejected the allogeneic cells and survived indefinitely. Spleens from these mice were virtually free of H-2Kd-positive cells (0.51 +/- 0.21%) by day 7. In contrast, C57BL/6 mice treated with 10 mg/kg/day s.c. of CsA all died from the L1210 challenge (mean survival time of 9 +/- 1 days). Spleens from mice treated in this manner contained 11.02 +/- 3.31% H-2Kd-positive cells on day 7. There was a direct correlation between the dose of CsA administered (7.5-50 mg/kg/day) and the percentage of H-2Kd-positive cells in the spleen. We then compared the immunosuppressive activity of AM1 and CsA in this model. AM1 was purified from the urine of CsA-treated renal allograft recipients by a combination of preparative adsorption-desorption chromatography and preparative elution high-performance liquid chromatography. AM1 at a dose of 10 mg/kg/day exhibited no demonstrable immunosuppressive effect, and trough levels of AM1 on day 7 were only 36 +/- 4 ng/ml. Increasing the dose of AM1 to 50 mg/kg/day resulted in only 1.05 +/- 0.16% H-2Kd-positive cells in the spleens (P = NS) and a mean trough level of 221 +/- 27 ng/ml. In contrast, mice treated with 50 mg/kg/day of CsA exhibited 17.7 +/- 2.9% H-2Kd-positive cells in their spleens and a mean trough CsA level of 3036 +/- 277 ng/ml. The half-life of a single subcutaneous dose of 10 mg/kg of AM1 (4.6 hr) was significantly shorter than that of CsA (9.7 hr) in mice. Compared with CsA, the lack of immunosuppressive effect of AM1 in vivo therefore appears to be due to a combination of decreased immunosuppressive activity and increased rate of clearance in mice.

Advances in catecholamine and metabolite measurements for diagnosis of pheochromocytoma

Assessment of catecholamine production and excretion is important in the laboratory detection of pheochromocytoma, a rare but curable cause of hypertension. Advances in catecholamine and metabolite methodologies have enhanced the diagnostic acumen by increasing analytical sensitivity and eliminating many of the interferences observed with earlier methods. Estimation of urinary catecholamines metanephrine and vanillylmandelic acid is routinely used in the biochemical detection of pheochromocytoma and in monitoring the completeness of tumor excision as well as the possibility of recurrence. Traditional spectrophotometric and fluorometric methods for urinary catecholamines and their metabolites are being replaced by highly sensitive and selective chromatographic methods. The ability to quantify individual catecholamines and metanephrines by high-performance liquid chromatography is of particular value for detecting familial forms of the tumor that may secrete epinephrine. Plasma norepinephrine and epinephrine measurements are of additional diagnostic value in determining recent catecholamine release and response to clonidine suppression. For either urine or plasma measurements, appropriate patient preparation, sample collection, and method validation along with an understanding of the variable pattern of catecholamine secretion and metabolism in pheochromocytoma are essential. Advances in laboratory methodology and reference intervals for catecholamines for clinical interpretation are reviewed.

Advances in catecholamine and metabolite measurements for diagnosis of pheochromocytoma

Assessment of catecholamine production and excretion is important in the laboratory detection of pheochromocytoma, a rare but curable cause of hypertension. Advances in catecholamine and metabolite methodologies have enhanced the diagnostic acumen by increasing analytical sensitivity and eliminating many of the interferences observed with earlier methods. Estimation of urinary catecholamines metanephrine and vanillylmandelic acid is routinely used in the biochemical detection of pheochromocytoma and in monitoring the completeness of tumor excision as well as the possibility of recurrence. Traditional spectrophotometric and fluorometric methods for urinary catecholamines and their metabolites are being replaced by highly sensitive and selective chromatographic methods. The ability to quantify individual catecholamines and metanephrines by high-performance liquid chromatography is of particular value for detecting familial forms of the tumor that may secrete epinephrine. Plasma norepinephrine and epinephrine measurements are of additional diagnostic value in determining recent catecholamine release and response to clonidine suppression. For either urine or plasma measurements, appropriate patient preparation, sample collection, and method validation along with an understanding of the variable pattern of catecholamine secretion and metabolism in pheochromocytoma are essential. Advances in laboratory methodology and reference intervals for catecholamines for clinical interpretation are reviewed.

The clinical significance of cyclosporine metabolites

Cyclosporine (CsA) is extensively metabolized, with over 14 metabolites having been characterized to date. The confirmation of structure and purity is a prerequisite for studies involving CsA metabolites. Analytical techniques such as fast atom bombardment/mass spectroscopy (FAB/MS), tandem mass spectrometry (MS), 1H- and 13C-nuclear magnetic resonance (NMR) can be used for such purposes. In vitro experiments indicate that metabolites are considerably less immunosuppressive and toxic than CsA. In vivo studies have been hampered by sufficient quantities of metabolites and a suitable animal model. Preliminary results in the rat suggest that CsA metabolites are less immunosuppressive and toxic than CsA, although these results must be confirmed using a more suitable animal model. Present data indicate that the routine monitoring of metabolites is not warranted in transplant patients, although additional information is required to confirm these findings.

Candidate reference method for determining creatinine in serum: method development and interlaboratory validation

We describe a "high-performance" liquid chromatographic (HPLC) method for accurately determining creatinine in serum. After prechromatographic precipitation of protein, we performed isocratic ion-exchange chromatography with ultraviolet detection (234 nm). Analytical results showed linearity up to 1770 mumol/L, a detection limit of 22 mumol/L, an average analytical recovery of 101%, and a CV ranging from 3% to 11%. We used certified human serum (National Institute of Standards and Technology), and additional lyophilized serum pools also assayed by definitive isotope-dilution mass spectrometry, to validate the accuracy of the HPLC method. In addition, the isocratic HPLC results showed close agreement with those obtained with a step-gradient HPLC method. We also compared the isocratic HPLC method with alkaline picrate and enzymatic methods. Our findings with samples from nonuremic, uremic, and diabetic ketoacidotic patients confirmed the positive bias previously reported with the alkaline picrate method. Interlaboratory transferability of the method was demonstrated with various commercial instruments and analytical columns. We evaluated column stability and possible interference from endogenous or exogenous compounds. On the basis of our analytical findings, we recommend the isocratic HPLC method as a candidate Reference Method for determining creatinine in serum.

Candidate reference method for determining creatinine in serum: method development and interlaboratory validation

We describe a "high-performance" liquid chromatographic (HPLC) method for accurately determining creatinine in serum. After prechromatographic precipitation of protein, we performed isocratic ion-exchange chromatography with ultraviolet detection (234 nm). Analytical results showed linearity up to 1770 mumol/L, a detection limit of 22 mumol/L, an average analytical recovery of 101%, and a CV ranging from 3% to 11%. We used certified human serum (National Institute of Standards and Technology), and additional lyophilized serum pools also assayed by definitive isotope-dilution mass spectrometry, to validate the accuracy of the HPLC method. In addition, the isocratic HPLC results showed close agreement with those obtained with a step-gradient HPLC method. We also compared the isocratic HPLC method with alkaline picrate and enzymatic methods. Our findings with samples from nonuremic, uremic, and diabetic ketoacidotic patients confirmed the positive bias previously reported with the alkaline picrate method. Interlaboratory transferability of the method was demonstrated with various commercial instruments and analytical columns. We evaluated column stability and possible interference from endogenous or exogenous compounds. On the basis of our analytical findings, we recommend the isocratic HPLC method as a candidate Reference Method for determining creatinine in serum.

Assessment of renal function by inulin clearance: comparison with creatinine clearance as determined by enzymatic methods

We compared creatinine clearances determined by enzymatic (Kodak Ektachem 700 single-slide, Boehringer Mannheim creatinine PAP) and nonenzymatic (Jaffé, HPLC) methods with glomerular filtration rate measured by inulin clearance in patients with varying degrees of renal function. The Kodak enzymatic assay gave values for creatinine 2 to 3 mg/L higher than the other methods. This resulted in significantly lower creatinine clearances than inulin clearances and creatinine clearances determined by the other methods. However, correlations between all methods for serum and urinary creatinine values and clearances were good. To avoid between assay (enzymatic vs nonenzymatic) discrepancies, manufacturers should agree to an acceptable standard of calibration under the usual conditions used with patients.

Assessment of renal function by inulin clearance: comparison with creatinine clearance as determined by enzymatic methods

We compared creatinine clearances determined by enzymatic (Kodak Ektachem 700 single-slide, Boehringer Mannheim creatinine PAP) and nonenzymatic (Jaffé, HPLC) methods with glomerular filtration rate measured by inulin clearance in patients with varying degrees of renal function. The Kodak enzymatic assay gave values for creatinine 2 to 3 mg/L higher than the other methods. This resulted in significantly lower creatinine clearances than inulin clearances and creatinine clearances determined by the other methods. However, correlations between all methods for serum and urinary creatinine values and clearances were good. To avoid between assay (enzymatic vs nonenzymatic) discrepancies, manufacturers should agree to an acceptable standard of calibration under the usual conditions used with patients.

Monoclonal antibodies for radioimmunoassay of cyclosporine: a multicenter comparison of their performance with the Sandoz polyclonal radioimmunoassay kit

The performance of a radioimmunoassay kit containing monoclonal specific and nonspecific antibodies to cyclosporine (Sandimmun-Kit; Sandoz Ltd., Basle, Switzerland) was compared with that of the original Sandoz polyclonal radioimmunoassay kit (Ciclosporin RIA-Kit). A total of 1320 blood and plasma samples from patients receiving cyclosporine after kidney, heart, liver, and bone-marrow transplantation were analyzed at six centers. For blood samples the median result on using the specific assay was about 50% of the polyclonal assay result after kidney and bone-marrow transplantation, about 33% after heart and liver transplantation; comparable figures for plasma samples were 70 and 40%. The monoclonal nonspecific-antibody assay produced results 10% to 140% higher than polyclonal-assay results, depending on sample matrix and transplant indication; the largest difference was seen in samples from heart- and liver-transplant recipients. Evidently the specific-antibody assay provides a convenient alternative to high-performance liquid chromatography for specific measurement of the drug, but the role of the new nonspecific antibody, possessing an even broader spectrum of cross-reactivity with cyclosporine metabolites than the original polyclonal antiserum, has yet to be defined.

Monoclonal antibodies for radioimmunoassay of cyclosporine: a multicenter comparison of their performance with the Sandoz polyclonal radioimmunoassay kit

The performance of a radioimmunoassay kit containing monoclonal specific and nonspecific antibodies to cyclosporine (Sandimmun-Kit; Sandoz Ltd., Basle, Switzerland) was compared with that of the original Sandoz polyclonal radioimmunoassay kit (Ciclosporin RIA-Kit). A total of 1320 blood and plasma samples from patients receiving cyclosporine after kidney, heart, liver, and bone-marrow transplantation were analyzed at six centers. For blood samples the median result on using the specific assay was about 50% of the polyclonal assay result after kidney and bone-marrow transplantation, about 33% after heart and liver transplantation; comparable figures for plasma samples were 70 and 40%. The monoclonal nonspecific-antibody assay produced results 10% to 140% higher than polyclonal-assay results, depending on sample matrix and transplant indication; the largest difference was seen in samples from heart- and liver-transplant recipients. Evidently the specific-antibody assay provides a convenient alternative to high-performance liquid chromatography for specific measurement of the drug, but the role of the new nonspecific antibody, possessing an even broader spectrum of cross-reactivity with cyclosporine metabolites than the original polyclonal antiserum, has yet to be defined.

Determination of cyclosporine concentrations with monoclonal antibodies

We measured cyclosporine in whole blood from normal volunteers administered single oral doses of the drug and from two renal-transplant patients on immunosuppressive maintenance therapy, by liquid chromatography (I) and by radioimmunoassay with use of nonspecific polyclonal (II), specific monoclonal (III), and nonspecific monoclonal (IV) antibodies. Concentrations determined by III were equivalent to I, irrespective of cyclosporine dose, concentration, time after dose, or time after transplant. Concentrations determined by II and IV were consistently higher than those by I, owing to cross reactivity with metabolites. Ratios of values by II and IV to those by I increased from less than 1.5 to about 3-4 between 0.5 and 12 h after a single cyclosporine dose, owing to differences in rates of appearance and disappearance of cyclosporine and cross-reacting metabolites, though for the constant 12-h dose intervals in the two renal-transplant patients at steady state these ratios (most within the range 3-4) were relatively stable. Ratios of concentrations measured by IV to those by II (mean of 1.2 for single-dose data, most within the range of 1.2 to 1.5 at steady state) were unaffected by time after dose or time after transplant, suggesting that, despite certain cross-reactivity differences between the two nonspecific antibodies, results are proportional throughout therapy. We therefore propose that III and IV offer alternatives, respectively, to the currently used I and II for cyclosporine monitoring.

Determination of cyclosporine concentrations with monoclonal antibodies

We measured cyclosporine in whole blood from normal volunteers administered single oral doses of the drug and from two renal-transplant patients on immunosuppressive maintenance therapy, by liquid chromatography (I) and by radioimmunoassay with use of nonspecific polyclonal (II), specific monoclonal (III), and nonspecific monoclonal (IV) antibodies. Concentrations determined by III were equivalent to I, irrespective of cyclosporine dose, concentration, time after dose, or time after transplant. Concentrations determined by II and IV were consistently higher than those by I, owing to cross reactivity with metabolites. Ratios of values by II and IV to those by I increased from less than 1.5 to about 3-4 between 0.5 and 12 h after a single cyclosporine dose, owing to differences in rates of appearance and disappearance of cyclosporine and cross-reacting metabolites, though for the constant 12-h dose intervals in the two renal-transplant patients at steady state these ratios (most within the range 3-4) were relatively stable. Ratios of concentrations measured by IV to those by II (mean of 1.2 for single-dose data, most within the range of 1.2 to 1.5 at steady state) were unaffected by time after dose or time after transplant, suggesting that, despite certain cross-reactivity differences between the two nonspecific antibodies, results are proportional throughout therapy. We therefore propose that III and IV offer alternatives, respectively, to the currently used I and II for cyclosporine monitoring.

Prevention of diabetes in BB rats by intermittent administration of cyclosporine

The successful prevention of spontaneous autoimmune diabetes in biobreeding (BB) rats--the closest animal model to human type I diabetes mellitus--by daily administrations of cyclosporine (CsA) has prompted clinical trials of CsA immunosuppression in human diabetes. Although remissions from hyperglycemia have been achieved in human subjects, nephrotoxicity and recurrence of diabetes after discontinuation of CsA have been observed. Therefore we studied the biologic efficacy of intermittent administration of CsA, a theoretically less dangerous immunosuppressive protocol, in the prevention of spontaneous diabetes in the BB rat. Beginning at 30 to 49 or 50 to 55 days of age, treated animals (n = 86) received daily injections of CsA (15 mg/Kg) for 2 weeks (induction phase) and then twice weekly (maintenance phase) until 160 days of age. A third group of animals (n = 31) received daily CsA for 14 days only. Control littermates (n = 121) were not injected. All animals were followed to 275 days of age. Intermittent administration of CsA was determined to be a biologically effective regimen in the prevention of spontaneous diabetes in the BB rat. Blood levels of CsA and the major CsA metabolites were undetectable intermittently during the course of therapy. Major complications associated with CsA immunosuppression (nephrotoxicity, malignancy, and infection) were not associated with the intermittent CsA protocol. We conclude that spontaneous diabetes can be delayed and often permanently prevented by intermittent administration of CsA. This immunosuppressive regimen deserves further consideration as a biologically effective, but theoretically less toxic, therapeutic regimen.

In vitro immunosuppressive properties of cyclosporine metabolites

The in vitro biological activity of cyclosporine (CsA) and four of its metabolites (M1, M8, M17, and M21) was determined. M1, M17, and M21 are primary metabolites, while M8 is a secondary metabolite derived from either M1 or M17. The order of inhibitory activity in production assays was phytohemagglutinin (PHA), concanavalin A (ConA), mixed lymphocyte culture (MLC), and interleukin-2 (IL-2) CsA greater than M17 greater than M1 greater than M21 much greater than M8. In the PHA assay, CsA was significantly more inhibitory than M17, but in Con A and MLC assays, the inhibitory activity of M17 approached that of CsA. More importantly, M17 and M1 inhibited the production of IL-2 in the MLC to the same extent as CsA. M21 was significantly less inhibitory than either M17 or M1, and M8 appeared to be largely devoid of biological activity. These experiments demonstrate that single hydroxylations of amino acids 1 (M17) and 9 (M1) do not significantly affect the ability of the molecule to block IL-2 production, but hydroxylation of both amino acids renders the molecule virtually inactive. In addition, the presence of the N-methyl group on amino acid 4 appears to be very important, since removal of this group (M21) greatly diminishes the immunosuppressive activity.

Immunosuppressive metabolites of cyclosporine in the blood of renal allograft recipients

Cyclosporine levels by radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC) were monitored in serial blood samples (n = 177) from 11 renal allograft recipients. HPLC analysis revealed three primary metabolites of CsA (M17, M1, and M21) in peak and trough blood samples; M17 was the preponderant metabolite. In 4 patients on whom serial metabolite assays were performed, M17 was found in the blood at 86-2004 ng/ml; M1 and M21 were found at up to 100 ng/ml. The immunosuppressive properties of purified metabolites M1, M17, M21, and M8 (which was not detected in the blood) were compared with CsA. M17--and, to a lesser extent, M1 and M21--were found to inhibit the in vitro response of human mononuclear cells in the mixed leukocyte culture and in mitogen (phytohemagglutinin [PHA], concanavalin A [Con A], and pokeweed mitogen [PWM]) assays at 1000 ng/ml. M8 exhibited no in vitro inhibitory activity. M17 was further tested at 10-1000 ng/ml in PHA and mixed lymphocyte culture (MLC) assays. M17 had considerably less inhibitory activity (12-43%) than CsA (18-70%) in the PHA assay. However, in MLC experiments M17 blocked the proliferative response by 39-72% at 100-800 ng/ml, which approached the degree of inhibition exhibited by CsA (63-87%). In 34 of 37 (92%) patient blood samples, the level of metabolite M17 was found to exceed the parent drug level and could not be measured accurately by RIA. The observed in vitro immunosuppressive activity of metabolites (particularly M17) and their presence in the blood of renal allograft recipients suggest a possible role for these metabolites in the immunopharmacology of CsA.

Effect of hematocrit on cyclosporine (cyclosporin A) in whole blood and plasma of renal-transplant patients

Cyclosporine concentrations in whole blood and plasma were determined in 25 samples from renal-transplant patients. The portion of cyclosporine carried in plasma varied widely, from 9 to 58%. Radioimmunoassay and liquid chromatography both revealed a statistically significant inverse correlation between hematocrit and the plasma fraction of cyclosporine in the circulating blood. Regression analysis indicates that a 10% increase in hematocrit would decrease the portion of cyclosporine in plasma by 12 to 14%. Studies with cyclosporine-supplemented samples further demonstrated an effect of hematocrit on the drug concentration in plasma without a corresponding effect on the concentration in whole blood. The distribution of cyclosporine between plasma and erythrocytes was unaffected by plasma cholesterol and triglycerides for these transplant patients.

Effect of hematocrit on cyclosporine (cyclosporin A) in whole blood and plasma of renal-transplant patients

Cyclosporine concentrations in whole blood and plasma were determined in 25 samples from renal-transplant patients. The portion of cyclosporine carried in plasma varied widely, from 9 to 58%. Radioimmunoassay and liquid chromatography both revealed a statistically significant inverse correlation between hematocrit and the plasma fraction of cyclosporine in the circulating blood. Regression analysis indicates that a 10% increase in hematocrit would decrease the portion of cyclosporine in plasma by 12 to 14%. Studies with cyclosporine-supplemented samples further demonstrated an effect of hematocrit on the drug concentration in plasma without a corresponding effect on the concentration in whole blood. The distribution of cyclosporine between plasma and erythrocytes was unaffected by plasma cholesterol and triglycerides for these transplant patients.

Liquid chromatographic assay of ceftizoxime in sera of normal and uremic patients

The application of high-pressure liquid chromatography assays for cephalosporin serum concentrations is difficult in uremic patients because of interference from nondialyzable substances. We developed a high-pressure liquid chromatography method for determining the serum concentration of ceftizoxime in normal and uremic patients. The method involves protein precipitation with acetonitrile, followed by removal of the acetonitrile with dichloromethane. Separation was accomplished with a reverse-phase (C-18) column and a mobile phase of 13% acetonitrile and 2.8% acetic acid. UV detection at 310 nm was used to monitor the peaks. This assay produced a linear relationship between peak height ratio and ceftizoxime concentration from 1.5 to 100 micrograms/ml. Samples from 30 patients were assayed by this method and by a bioassay, with a good correlation of results (r = 0.9832). The method was applicable equally to normal and uremic serum samples.

Liquid-chromatographic evaluation of age-related changes in the urinary excretion of free catecholamines in pediatric patients

Pediatric patients (to age 18) without neuroblastoma show an age-related decrease in urinary excretion of each of the catecholamines--epinephrine, norepinephrine, and dopamine--in relation to creatinine excretion. From these data, I have developed reference intervals for pediatric age groups. Application of these ranges to seven patients with neuroblastoma and ganglioneuroblastoma indicated a high clinical sensitivity for the urinary dopamine determination but significant false-negative results for epinephrine and norepinephrine.

Liquid-chromatographic evaluation of age-related changes in the urinary excretion of free catecholamines in pediatric patients

Pediatric patients (to age 18) without neuroblastoma show an age-related decrease in urinary excretion of each of the catecholamines--epinephrine, norepinephrine, and dopamine--in relation to creatinine excretion. From these data, I have developed reference intervals for pediatric age groups. Application of these ranges to seven patients with neuroblastoma and ganglioneuroblastoma indicated a high clinical sensitivity for the urinary dopamine determination but significant false-negative results for epinephrine and norepinephrine.