Radioimmunoassay for hydroxyphosphinyl-3-hydroxybutanoic acid (SQ 33,600), a hypocholesterolemia agent.

A specific and sensitive radioimmunoassay (RIA) for the measurement of SQ 33,600 in biological fluids has been developed. The assay utilizes a SQ 33,600 polyclonal antibody, [125I]iodohistamine-SQ 33,600 radiolabel, and standards in serum. Satisfactory zero binding and sensitivity were obtained after an overnight incubation at 4 degrees C. Separation of the antibody-bound and free radiolabel was achieved by employing polyethylene glycol-goat anti-rabbit gamma-globulin (PEG-GARG) separant. A quantitative recovery in serum and urine of the exogenous analyte was obtained at all concentrations of SQ 33,600 tested. Intra-assay coefficients of variation (CVs) were 6.19 and 5.57% for the low and high controls, respectively. Interassay CVs were 6.64 and 6.06% for the low and medium controls, respectively. Results from the parallelism studies were acceptable for both serum and urine samples. Comparison of results from samples which were assayed by RIA and high-performance liquid chromatography (HPLC) demonstrated a significant correlation (r = 0.994; HPLC = 1.09 RIA + 57.98; n = 45). The present RIA has been successfully used to assay clinical specimens from pharmacokinetic studies.

A specific radioimmunoassay for the measurement of gadoteridol, a contrast agent for magnetic resonance imaging in biological fluids.

Gadoteridol, a nonionic gadolinium chelate, is currently being evaluated for contrast-enhanced magnetic resonance imaging. A radioimmunoassay (RIA) has been developed for the measurement of gadoteridol in biological fluids. The RIA has a range of 0 to 25 micrograms/mL and has the sensitivity to detect 0.05 microgram/mL of gadoteridol. Satisfactory zero binding and sensitivity were obtained after an overnight incubation at 4 degrees C. Separation of the antibody-bound and free radiolabel was achieved with 12.5% polyethylene glycol. A quantitative recovery of the exogenous analyte was obtained at all concentrations of gadoteridol tested. Linearity in both serum and urine was satisfactory. Intraassay coefficients of variation were 6.4 and 2.8% for the low and medium controls, respectively. Interassay coefficients of variation were 5.4, 3.8, and 12.2% for the low, medium, and high controls, respectively. Cross reactivities of the ligand 5 and the calcium salt 6 were 37 and 29%, respectively. Clinical samples from the ascending dosage studies were analyzed by the gadoteridol RIA. The results obtained from the serum specimens demonstrated an excellent linear proportionality between drug concentration in blood and administered dosage of gadoteridol. Cumulative urinary excretion data showed that 94% of the drug was excreted in the urine within 24 h.

A radioimmunoassay for the new antiviral agent 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil.

A specific and sensitive radioimmunoassay (RIA) for the measurement of 1-beta-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil (BV-araU) in biological fluids has been developed. The assay has a range of 2.5-1,000 ng/ml and 10-1,000 ng/ml for serum and urine, respectively, and has the sensitivity to detect 2.5 and 25 ng/ml of BV-araU in serum and urine, respectively. A satisfactory zero binding and sensitivity were obtained after an overnight incubation at 4 degrees C. Separation of the antibody-bound and free ligand was achieved by employing polyethylene glycol-goat anti-rabbit gamma globulin separant. A quantitative recovery of the exogenous analyte was obtained at all concentrations of BV-araU tested. The assay is specific for the parent drug and is not affected by the presence of its metabolite, BV-U (bromovinyl uracil) or serum components (nucleotides, nucleosides, or sugars). Intraassay coefficients of variation were 3.1-4.4% and 2.5-4.2% for serum and urine controls, respectively. Interassay variability was < 8.6% for all serum and urine controls. Linear regression analysis showed that the correlation between RIA and high-pressure liquid chromatography was excellent (r = 0.997). The ascending dosage studies have been analyzed by the BV-araU RIA, and results indicate that the values of area under the serum concentration-time curve increased proportionally with the administered dose of BV-araU up to 80 mg. Cumulative urinary excretion data showed that approximately 50% of unchanged BV-araU was excreted in the urine within 24 h.

Radioimmunoassay for ceronapril, a new angiotensin-converting enzyme inhibitor, and its application to a pharmacokinetic study in healthy male volunteers.

Ceronapril is a member of a new chemical class of angiotensin-converting enzyme inhibitors being developed by The Bristol-Myers Squibb Pharmaceutical Research Institute. A radioimmunoassay (RIA) has been developed for the measurement of ceronapril in biological fluids. The RIA has a range of 0 to 500 ng/ml and has the sensitivity to detect 1.0 ng/ml of ceronapril. Satisfactory zero binding and sensitivity were obtained after a 2-h incubation at room temperature or overnight at 4 degrees C. Separation of the antibody-bound and free radiolabel was achieved by employing polyethylene glycol-goat anti-rabbit gamma-globulin separant. A quantitative recovery of the exogenous analyte was obtained at all concentrations of ceronapril tested. Intraassay coefficients of variance (CV's) were 3.9% and 4.6% for the low and medium controls, respectively. A highly significant statistical correlation between RIA and [14C]TLRC was observed for both plasma and urine samples. Clinical samples from the ascending dosage studies have been analyzed by the ceronapril RIA. The maximum concentration and the area under the plasma concentration-time curve did not increase in a dose-proportional manner for doses above 100 mg.

Assays for plasma complement activation by x-ray contrast media.

Hemolytic complement activity and a C3a radioimmunoassay (RIA) were investigated for their ability to characterize contrast media (CM) with respect to complement activation. The CM tested were commercial formulations of diatrizoate, iodamide, iothalamate, ioxaglate, iohexol, and iopamidol. When plasma was exposed to CM, the hemolytic complement activity decreased and the C3a concentration increased. The C3a assay had a larger dynamic range and therefore more ability to discriminate among the CM. Using C3a data from pooled plasma or from individual donors' plasma, nonionic iopamidol (as Isovue 300) had lower complement-activating potential (P less than .005 and P greater than .05, respectively) than all of the ionic media based on diatrizoate, iothalamate, iodamide, and ioxaglate. The ranges of mean C3a values generated by saline, nonionic CM, and ionic CM were 48 to 60, 65 to 173, and 807 to 3272 ng C3a/50 microL, respectively. Complement activation was found to correlate with osmolality (r = 0.945, all media) and with molarity (r = 0.994, diatrizoates).

A predictive test for adverse reactions to contrast media. Preliminary results.

In a prospective study, whole blood samples drawn from patients prior to their being injected with contrast media were incubated with zymosan to activate the complement cascade. The samples were tested for various analytes, including C3a, thromboxane B2 (TxB2), beta thromboglobulin and platelet factor 4 (PF4). Of 207 patients receiving contrast media, only eight experienced reactions, which were mild. Levels of the platelet constituents were generally elevated in these patients. Specificity and sensitivity were 89% and 83%, respectively, for the combined TxB2 and PF4 radioimmunoassay data. Using the Wilcoxon-Mann-Whitney rank sum test, both PF4 and TxB2 were collected with RCM reactions at the R less than .05 level. Although preliminary, the results suggest that RCM reactions are predictable by the in vitro test procedures described.

Efferent enhancement of a methylcholanthrene-induced sarcoma transplantable in strain 13 guinea pigs.

The immunobiology of an antigenic methylcholanthrene-induced sarcoma (MC-D) of inbred strain 13 guinea pigs has been investigated. The induction of concomitant immunity by growing MC-D tumors was indicated by the suppression of small tumor inocula in the presence of a large tumor cell dose and by the regression of intradermal tumor nodules. Furthermore, it was demonstrated that this tumor was coated with antibody in vivo. Previous studies showed that MC-D tumors were infiltrated with killer T cells which were capable of complete tumor destruction in vitro, but could never induce spontaneous regression in vivo. On the basis of all these facts, antibody-mediated efferent enhancement is proposed to be the major escape mechanism of this tumor.

A microradioimmunoassay for antibodies to tumor-associated antigens.

A versatile microradioimmunoassay for the detection of antibodies to tumor-associated and other tissue antigens was described. The method involved: a) the preparation of solid-phase antigen with cultured (already adhered) or noncultured cells (sedimented by centrifugation) fixed to Micro-Test plates with neutral buffered formaldehyde or absolute methanol; b) the incubation of the antigen with test or control sera; and c) the incubation of the antigen with radioiodinated antiglobulin antibody. The nonspecific background of radioactivity was reduced to an acceptable level by the fixed cells being precoated in the wells with 0.5% bovine serum albumin in phosphate-buffered saline which was also used for the dilution of sera and labeled antiglobulin antibody. Tumor cells in primary cultures gave a high background, as compared to long-term cultures, which was due to the presence of immunoglobulins (most likely tumor-specific antibody). The specific antibody response to a syngeneic mouse tumor was demonstrated by this technique.