Blood radioimmunoassay

Medroxyprog esteroneAcetate. Accurate pharmacokinetic and metaboHsm studies on MPA have been difficult because the radioimmunoassays employed caimot differentiate between MPA and its metaboHtes (346). Comparison of MPA plasma levels assayed by hplc and radioimmunoassay show that radioimmunoassay may overestimate intact MPA concentrations by about fivefold (347). However, values of the mean elimination half-life of MPA were similar, being 33.8 and 39.7 h when measured by hplc and radioimmunoassay, respectively (347). Approximately 94% of MPA in the blood is bound to albumin (348). When taken orally, MPA is rapidly absorbed with Htde or no first-pass metaboHsm (13). Peak semm levels ate reached after 3 h. Steady state occurs after three days of daily adininistration (349). The pharmacokinetics of MPA when adininistered in a depot formulation have been described (350). 

Radiotracers have also been used extensively for the quantitative rnicrodeterrnination of blood semm levels of hormones (qv), proteins, neurotransmitters, and other physiologically important compounds. Radioimmunoassay, which involves the competition of a known quantity of radiolabeled tracer, usually I or H, with the unknown quantity of semm component for binding to a specific antibody that has been raised against the component to be deterrnined, is used in the rnicro deterrnination of physiologically active materials in biological samples (see Immunoassay). 

Human erythropoietin is a glycoprotein of 166 amino acids (molecular mass about 34 kDa). Its amount in plasma can be measured by radioimmunoassay. It is the major regulator of human erythropoiesis. Erythropoietin is synthesized mainly by the kidney and is released in response to hypoxia into the bloodstream, in which it travels to the bone marrow. There it interacts with progenitors of red blood cells via a specific receptor. The receptor is a transmembrane protein consisting of two different subunits and a number of domains. It is not a tyrosine kinase, but it stimulates the activities of specific... 

Blood samples were centrifuged at 1000 x g for 20 min at 0-4°. Ionized calcium levels were immediately determined in serum and urine samples using a calcium ion-selective electrode (Ionetics, Inc., Costa Mesa, CA) urine volumes were recorded. The remaining serum and urine were aliquoted for various analyses and stored at -40°. Serum insulin was analysed by radioimmunoassay (Amersham Corp., Arlington Heights, IL). Serum levels of total calcium, phosphorus and creatinine as well as urine creatinine were determined by colorimetric procedures using an automated analyzer (Centrifichem, Baker Instruments Corp., Pleasantville, NY). Glomerular filtration rates (GFR) were calculated from serum and urine creatinine data GFR = urine creatinine/serum creatinine. 

Other cytokines synthesised by activated neutrophils (but not bloodstream neutrophils) include interferon-a G-CSF and M-CSF. Interferon-a expression is stimulated by exposure of blood neutrophils to G-CSF (incubation times >3 h are required), but expression of this cytokine is not activated by exposure to either LPS or fMet-Leu-Phe. G-CSF induces 0.95- and 1.2-kb mRNA molecules, the latter transcript containing the message plus a 3 noncoding region. Synthesis of interferon-a protein (as determined by a radioimmunoassay) requires incubation times in excess of 6 h, and the functions of this cytokine include inhibition of neutrophil-colony formation and platelet formation in vitro. 

Radioimmunoassay. RIA caused a revolution in clinical diagnostics, providing a rapid, ultrasensitive method for the detection of nearly any agent to which an antibody could be developed. Sensitivity limits in the parts-per-trillion (pptr) or pg/mL are commonplace and RIAs are available for nearly every class of clinically relevant analyte including drugs, hormones, immunoglobulins, immune complexes, blood factors, microbes, viruses, and tumor antigens. 

Banks, W.A., J.B. Jaspan, and A.J. Kastin. 1997. Selective, physiological transport of insulin across the blood-brain barrier Novel demonstration by species-specific radioimmunoassays. Peptides 18 1257. 

Tracy PB, Eide LL, Bowie EJ, etal. Radioimmunoassay of factor V in human plasma and platelets. Blood 1982 60 59-63. 

Current research involves the use of radioimmunoassay to quantitate testosterone and estrogen in dried blood samples (22, 24). The ultimate goal of this research will be to determine the sexual origin of the stains. In the past, researchers have attempted this by identifying Barr bodies and Y chromosomes using differential fluorescence staining with quinacine however, these tests required a substantial amount of blood deposited as a thin film on a non-porous surface and are therefore limited in their application (19, 20, 21). The sensitivity and basic technique of radioimmunoassay will permit the analysis of bloodstains on virtually any surface and should also be applicable to very small ones. 

DNA is available in human sperm and in white blood cells. From these sources, it should be possible to obtain DNA to detect changes resulting from agents, such as alkylating agents, that react chemically to cause mutations. In experimental animals, this can be done easily with radioactive tracers.238 Very sensitive and precise radioimmunoassays being developed may greatly improve quantitative assessment, so that this technique could be applied to experimental animals and man. No practical chemical assay has been developed that can be... 

Free Thyroxine. Measurement of free T4 radioimmunoassay in dried blood samples has been found to be useful to avoid false-positive results for low TBG in neonatal hypothyroid screening. Enzyme immunoassay of free T4 in serum was developed by Weetall et al. (W7) and subsequently by us (16). 

TBG in dried blood samples on filter paper is stable for at least 1 month when kept dry at room temperature. The mean coefficients of variation are 6.6% (within assay) and 5.9% (between assays). The concentrations of TBG in dried blood samples determined by this method correlated well with those in serum determined by radioimmunoassay (r = 0.95) and by enzyme immunoassay (r = 0.96). This method is applicable for detecting patients with congenital TBG deficiency who do not need to be treated and avoids the false-positive results obtained on neonatal screening with T4. 

Pang et al. reported a successful mass screening for congenital adrenal hyperplasia by measuring 17a-hydroxyprogesterone in dried blood samples on filter paper (P2). They used radioimmunoassay but recently Arakawa et al. developed a chemiluminescence enzyme immunoassay of 17a-hy-droxyprogesterone for this purpose (A6). 

Cystic fibrosis is a lethal autosomal recessive disorder in Caucasians, with an incidence of 1 2000 in the general population. Newborn babies with this disease have increased serum trypsin concentrations. Thus, Crossley et al. developed a radioimmunoassay for human trypsin in dried blood samples on filter paper and used it for neonatal screening for this disease (C9). A non-isotopic immunoassay, such as enzyme immunoassay of trypsin, will be developed for this purpose. 

Atopic diseases including atopic dermatitis and bronchial asthma develop during the infantile period and are found to be predictable at birth by detecting a high immunoglobulin E (IgE) concentration in cord blood. Croner et al. reported a radioimmunoassay of IgE for screening for these disorders (C8). A method of enzyme immunoassay of IgE in serum has been developed (H6) and may be used for this purpose. 

Since radioimmunoassay has permitted the quantitation of substances present in concentrations as low as a few pg/ml of a biological fluid, and since the inherent selectivity of antibodies often make sample preparation requirements minimal and assay methodology simple, RIA has naturally been considered as a means for measuring blood levels of cannabinoid compounds. 

Hollander and co-workers [303—305] dealt with the problem in detail and developed a method for the isolation of hormones from blood, using Bio-Rad AG 50W-X2 (100—120 mesh) ion-exchange resin. Acylation with pivalic anhydride—methanol—triethylamine (20 1 1) was performed at 70°C for 10 min. The derivatives were purified with the aid of Amberlite IR-45 resin and benzene as a solvent. The dry residue was dissolved in 100 jul of benzene and 5 /il were injected directly on to a 60 cm X 4 mm I.D. column packed with 5% OV-1 on Chromosorb W HP after an isothermal period at 220°C for 12 min, the temperature was increased at 3°C/min up to 300°C. Calibration standards were injected immediately after the sample. Almost identical results were obtained for T3 by GC and radioimmunoassay [304], Other workers [306] applied the same procedure to the seeds and analysed pivalyl methyl esters of T3 and T4 on an 81 cm column packed with 3% of Dexsil on Chromosorb W HP at 305°C. 

Groups of 10-15 rats weighing 90-110 g are treated daily for 10 weeks with the candidate compound (omeprazole as standard at doses of 10 or 30 mg/kg p.o.). After treatment for 2, 4, 7, and 10 weeks, blood samples are collected under ether anesthesia by retro orbital puncture. Gastrin is determined by a commercially available radioimmunoassay kit. At the end of the study of 10 weeks, the animals are studied for their gastric acid output using the pylorus ligation (Shay technique). 

The flow of pancreatic juice and bile was tested before and after the experiment by means of an intravenous bolus of 5 pmol/kg secretin. Before the experiment the duodenum was continuously perfused at a rate of 2 ml/min for 435 min with isotonic saline containing phenol red (10 mg/1) as a marker. After drug treatment (intravenous infusion of gastrin-releasing peptide or duodenal HC1 perfusion) pancreatic and hepatic secretions were collected in 15-min periods and the volumes determined by weighing. Duodenal effluents were collected in 15-min periods and phenol red concentrations determined spectrophotometrically. Blood sampled were withdrawn for determination of secretin by radioimmunoassay. 

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