Can WR-2721 be improved upon?
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Amifostine↗
Biomedical subjects
L M Shaw
Publications and source records attributed to L M Shaw.
Pharmacokinetics of WR-2721.
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Amifostine↗
Macrophage interactions with laminin: PMA selectively induces the adherence and spreading of mouse macrophages on a laminin substratum.
The ability of thioglycollate (TG)-elicited mouse peritoneal macrophages to adhere to a laminin substratum has been studied. These cells do not adhere to laminin-coated (20 micrograms/ml) surfaces, but the addition of phorbol myristate acetate (PMA; 50 ng/ml) results in their rapid adherence and spreading on this substratum. TG-elicited and PMA-activated macrophages, however, can bind soluble laminin. Macrophages adhere to fibronectin-coated surfaces and tissue culture plastic without PMA stimulation, and PMA does not increase the number of cells that adhere to these surfaces. The predominant surface proteins that bind specifically to laminin-Sepharose exhibit an Mr of 67 and 36 kD, but the expression of these proteins does not increase after PMA stimulation. Laminin receptor antibodies immunoprecipitate the 67-kD protein from radiolabled surface lysates and are capable of blocking macrophage adherence to a laminin substratum. Indirect immunofluorescence microscopy indicates that PMA stimulation does not increase receptor expression, but that it may induce the aggregation of the receptor on the cell surface. PMA stimulation also promotes macrophage spreading and induces a reorganization of the actin cytoskeleton. Taken together, these data indicate the mechanism by which PMA promotes macrophage adherence to laminin does not involve increased 67-kD receptor surface expression, but that it is related to the changes in cytoskeletal and receptor surface organization that occur in response to PMA stimulation.
Animals↗
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.
Antibodies↗
The effect of phenobarbital and methylprednisolone on the biotransformation of cyclosporine in the rat.
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Animals↗
Predominance of native cyclosporine over metabolites in rat blood and tissue.
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Administration, Oral↗
Laboratory assessment of poisoning with a carbamate insecticide.
We discuss a case of a 17-year-old white male who intentionally ingested a tick and flea insecticide and was admitted to the emergency room unconscious, with signs and symptoms of cholinergic toxicity. Capillary gas chromatography and electron-impact mass fragmentographic analysis of the patient's urine and serum demonstrated the presence of poly-ethylene glycol and propoxur (o-isopropoxyphenyl N-methyl-carbamate), a carbamate-based cholinesterase inhibitor commonly used in insecticides. The patient fully recovered, but only after a complicated hospital course. We also discuss the laboratory assessment and clinical treatment of poisoning with carbamate and organophosphate insecticides.
Adolescent↗
The effect of changes in arterial CO2 tension on plasma lidocaine concentration.
The authors studied the effect of changes in arterial carbon dioxide tension on plasma lidocaine concentrations during a constant lidocaine infusion in eight healthy volunteers. With a PaCO2 of 41.4 +/- 0.9 mmHg (mean +/- SE), total plasma lidocaine concentrations were 3.97 +/- 0.20 microgram X ml-1. There was no significant change associated with hypercarbia (PaCO2 = 55.7 +/- 1.5 mmHg, lidocaine = 3.93 +/- 0.18 microgram X ml-1) or hypocarbia (PaCO2 = 19.5 +/- 1.4 mmHg, lidocaine = 4.29 +/- 0.25 microgram X ml-1), despite the known effects of changes in CO2 tension on hepatic blood flow and lidocaine protein binding. During hypercarbia, plasma lidocaine binding decreases while total plasma lidocaine remains essentially constant; therefore, increased CO2 tensions could cause toxicity if total lidocaine concentrations were in the high therapeutic range (5 micrograms X ml-1). Four subjects experienced transient symptoms of mild lidocaine toxicity during acute increases in carbon dioxide tension.
Adult↗
Hydrolysis of WR2721 by mouse liver cell fractions.
A study of the dephosphorylation of WR2721 by broken cell preparations of mouse liver revealed the presence of at least two distinctive activities. One activity was inactivated by heat treatment and was present in the nuclear and microsomal fractions. It had an optimum pH at 9 and was inhibited by sodium vanadate, EDTA, and phenylalanine. Further subcellular fractionation demonstrated the localization of this activity in plasma membrane. A second WR2721 hydrolysis activity was detected in the cytosol fraction (postmicrosomal supernatant), which changed little with pH over the range of 5 to 10; sodium vanadate did not inhibit it. The cytosolic activity in response to heat treatment was complicated since there was an initial decrease followed by an increase in catalytic activity as a function of time at 55 degrees C. Enzyme kinetic analysis of the plasma membrane-associated activity in the microsomal fraction was performed, and Km and Vmax values of 12.5 and 69.9 nmol/min/mg protein, respectively, were obtained.
Amifostine↗
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.
Animals↗
The pharmacokinetic and pharmacodynamic effects of varying the free fraction of disopyramide.
We have evaluated the influence of several factors on the binding of disopyramide to protein in human serum using a new ultrafiltration system and the enzyme multiplied immunoassay technique (EMIT) for disopyramide immunoassay. From these studies and those of other investigators, we conclude that the most significant in vivo factors influencing disopyramide binding in human serum are total disopyramide concentration, the concentration of alpha 1-acid glycoprotein, and the concentration of mono-N-dealkyldisopyramide. Significant variation in binding occurs in patients whose total disopyramide concentration is within the therapeutic range. The proportion of free disopyramide ranged from 16% to 54% in the sera of 50 cardiac patients whose total disopyramide concentration ranged from 0.5 to 5.8 mcg/ml. Since there is so much variation in the proportion of disopyramide that is free, and since it is the unbound form of the drug that is pharmacologically active, it is likely in patients whose arrhythmia responds to disopyramide therapy that unbound drug concentration will be a better indicator of drug efficacy and toxicity than will be total drug concentration. To test this hypothesis, we are investigating the relationship between steady state total and unbound disopyramide plasma levels in patients with supraventricular or ventricular arrhythmias, and pharmacologic response as determined by standard intracardiac electrophysiologic studies.
Blood Proteins↗
Hydrolysis of S-2-(3-aminopropylamino)ethylphosphorothioate (WR-2721).
The hydrolysis reaction of S-2-(3-aminopropylamino)ethylphosphorothioate (WR-2721), a radioprotective agent currently undergoing clinical trials, was studied under a variety of experimental conditions in order to provide more complete data and to reconcile significant differences found between two previous studies. 31P NMR spectroscopy was primarily used to follow the reaction, but comparable results were also obtained in parallel studies using a spectrophotometric technique and a technique involving liquid chromatography with electrochemical detection, in which the free sulfhydryl product, 2-(3-aminopropylamino)ethanethiol (WR-1065), was measured. Upon hydrolysis, inorganic phosphate and the free sulfhydryl group were formed by cleavage of the P-S bond. The reaction rate versus pH profile at 30 degrees in 42.5 mM buffer, mu = 127.5 mM, showed primarily hydrolysis of the monoanion, with an acid-catalyzed reaction below pH 1.5 to 2.0 involving the neutral species of the ester. The energy of activation at pH 4.0 in 42.5 mM acetate buffer was 25.7 kcal/mole (23.1 kcal/mole by liquid chromatography with electrochemical detection). The entropy of activation at pH 4.0, 36 degrees was positive, and there was a deuterium isotope effect on the reaction. A small buffer effect on the rate of the reaction at pH 4.0 and pH 5.0 was found to include contributions from both general acid and general base catalysis. These data are consistent with a mechanism for hydrolysis of the monoanion involving a partially rate-determining proton transfer to the sulfur atom and the formation of metaphosphate ion, which is rapidly hydrolyzed to inorganic phosphate.
Amifostine↗
Evaluation of prostate-specific antigen and prostatic acid phosphatase as prostate cancer markers.
Prostate-specific antigen (PSA) and prostatic acid phosphatase (PAP) have been evaluated in patients with prostate cancer, benign prostatic hypertrophy (BPH), and prostatitis. PSA has proved to be diagnostically more sensitive than PAP for the detection of prostate cancer: 95.0 per cent vs 60.0 per cent for 40 newly diagnosed cancer cases, and 97.1 per cent vs 65.7 per cent for 35 relapsed cases. This also holds true for those patients with early-stage disease: 71.4 per cent vs 0 per cent for 7 Stage A1 cases. The specificities of PSA and PAP are comparable, 96.8 per cent vs 98.9 per cent, respectively. PSA is also more sensitive for monitoring therapy, since it usually rises before PAP and always precedes clinical signs of relapse. Although PSA may be elevated more frequently than PAP in some patients with BPH and prostatitis, it is postulated that these patients with elevated serum PSA and normal serum PAP may fall into a high-risk sub-population which may have early prostate cancer or precancerous conditions not easily detectable by current clinical and diagnostic techniques. Our data suggest PSA is a sensitive useful tumor marker for the diagnosis and management of prostate cancer. In addition, PAP, in combination with PSA, may serve as a useful adjunct for differential diagnosis and confirmation of advanced stage prostate cancer.
Acid Phosphatase↗
Modification of WR-2721 toxicity and radioprotection by an inhibitor of alkaline phosphatase.
We used levamisole, an inhibitor of alkaline phosphatase, to study the role of that enzyme in mediating the metabolic activation, toxicity, and radioprotection of WR-2721 in intact mice. We found the toxicity of WR-2721 was slightly decreased by prior subcutaneous (SQ) injection of 40 mg/kg of levamisole. In studying the effect of levamisole on WR-2721 radioprotection, we found that intraperitoneal (i.p.) injection of levamisole had little or no effect on radioprotection of the gastrointestinal and the hematopoietic systems. Even this small reduction of protection was due in part to the toxicity of levamisole as demonstrated when levamisole was injected following, rather than before, WR-2721-radiation treatment. To determine whether levamisole inhibited the activation (i.e., dephosphorylation) of WR-2721 to WR-1065, we assayed WR-1065 in the jejunum using an HPLC electrochemical assay. SQ injection of 75 mg/kg levamisole 10 min prior to WR-2721 reduced the WR-1065 observed 10 min after WR-2721 administration by 37%. In conclusion, levamisole appears to be too toxic and non-specific to be useful in studying and regulating the metabolism, toxicity and radioprotection of WR-2721.
Alkaline Phosphatase↗
Human pharmacokinetics of WR-2721.
The pharmacokinetic properties of WR-2721 were investigated in 13 cancer patients given a 150 mg/M2 intravenous bolus dose of the drug. An average plasma clearance value of 2.17 L/min was obtained. Very little of the drug or the two metabolites, WR-1065 and WR-33278, were excreted in urine obtained after the blood collection schedule. Plasma concentrations of WR-2721 decreased by 94% within 6 minutes of drug administration. The mean value of 6.44 L obtained for the steady-state volume of distribution indicates that the extravascular space occupied by the drug is small. These observations suggest that in human cancer patients, WR-2721 is rapidly taken up by tissues and converted to metabolites.
Amifostine↗
Effect of plasma exchange on phenytoin plasma concentration.
The effect of plasma exchange on the concentrations of total and unbound phenytoin (DPH) was determined in one normal subject and four patients undergoing therapeutic plasma exchange (PE). The average percentage of plasma exchanged ranged from 57 to 70% among the five patients studied. The reduction in DPH concentration was more variable and ranged from 10 to 16%. However, the extent of reduction within each patient for both total DPH and "free" DPH serum concentrations was minimal; in addition, the ratio of free to total DPH remained virtually unchanged by plasma exchange. Thus, the replacement of endogenous albumin with exogenous albumin, which is an integral part of therapeutic plasma exchange, does not appear to alter DPH binding. Our findings indicate that rapid equilibration of DPH occurs between the intra- and extravascular compartments and that for the occasional plasma exchange procedure, dose adjustment does not appear indicated.
Blood Component Removal↗
Diagnostic accuracy of four assays of prostatic acid phosphatase. Comparison using receiver operating characteristic curve analysis.
We compared the diagnostic characteristics of four assays of prostatic acid phosphatase by two methods. In the first analysis, receiver operating characteristic (ROC) curves were developed and the areas under the curves were calculated. In the second analysis, the sensitivity of each assay was compared with the sensitivities of the other assays with specificities set at equal levels. One or more assays were performed in 1,298 patients; 141 underwent all four assays. Pairwise comparisons of the areas under the ROC curves showed no significant differences. No differences were found in the sensitivities of the four assays when the upper limits of normal were selected to provide equal specificities. We conclude that there is little difference in diagnostic accuracy among the prostatic acid phosphatase assays. Our findings contrast with previous studies that used only one upper limit of normal and that found some assays to be superior to others. Receiver operating characteristic curve analysis corrects for the bias introduced by the choice of an upper limit of normal.
Acid Phosphatase↗
Modification of lidocaine protein binding with CO2.
Using new, specially designed ultrafiltration devices and an enzyme immunoassay technique, the authors determined the effect of carbon dioxide tension on the fractional binding of lidocaine to human plasma proteins. Identical samples of serum at therapeutic (2.2 micrograms X ml-1) and toxic (6.8 micrograms X ml-1) lidocaine concentrations were tonometered at 37 degrees C to CO2 tensions between 0.13 and 10.7 kPa (1.0 to 80.5 mmHg). The fraction of unbound lidocaine increased linearly with increasing pCO2 (r = 0.93, p less than 0.001). These changes help to explain the increased central nervous system toxicity of lidocaine associated with hypercarbia.
Blood Proteins↗