[5] 125Iodinated tracers for hapten-specific radioimmunoassays. Immunochemical Techniques: Part B. Elsevier; 1981. pp. 79-112. [DOI: 10.1016/0076-6879(81)73058-1]

Papaverine effects on PGI2 and TXA2 release from the canine vascular wall

Operative manipulation of blood vessels might lead to spasm, thereby destroying the endothelial cell function: the spasm can be prevented by the vasodilator papaverine. To study if this was mediated via the prostanoid pathway the following investigation was undertaken: canine jugular veins and carotid arteries were dissected with or without papaverine. Vessel segments were then perfused with Hank's balanced salt solution for five times 15 min. Prostacyclin was measured as the stable degradation product 6-keto-PGF1 alpha and thromboxane as TXB2, by radioimmunoassay. Control arterial segments' 6-keto-PGF1 alpha release was initially 129.5 + 20.1 pg/mm2/15 min, and 29.7 + 10.4 after 60 min (p less than 0.05 vs initial value) and responded to arachidonic acid (AA) with an increase to 139.2 +/- 23.1 pg/mm2/15 min (p less than 0.05). Segments treated with papaverine had the same release as the controls. In venous segments there was a lower initial release (p less than 0.05) from segments given papaverine than from controls, but this was more likely an effect of papaverine on the assay. There was no difference in release of prostacyclin from segments given papaverine in the perfusate compared to controls when using 125I tracer. When using 3H tracer including absorption of free antigen to dextran coated charcoal, papaverine displaced the free tracer giving artificially low values. There was no effect of papaverine given intraoperatively on the TXB2 release, neither from arteries nor from veins. In another experiment the vessel wall tension was examined and the cyclooxygenase inhibitor diclofenac did not inhibit the vasodilating effect of papaverine.(ABSTRACT TRUNCATED AT 250 WORDS)

Oestradiol assays: applications and guidelines for the provision of a clinical biochemistry service

This paper reports on the provision of a clinical biochemistry service for serum oestradiol. The pathophysiology and recognised applications of oestradiol assays are discussed and the current availability of assay reagents and methodologies reviewed. Data are presented on the analytical performance of assays for serum oestradiol in the UK External Quality Assessment Scheme (UKEQAS) and general guidance is offered to laboratories providing a diagnostic service for this analyte.

Structural aspects of steroid-antibody specificity

The paper gives a review of the immunogens most frequently used for preparing antibodies against steroid haptens. The structural concepts of immunological specificity and complementarity are applied to a description of the formation of antibodies in immunized animals and the binding mechanisms of steroid-antibody interactions in systems in vitro. Recent experimental findings show that Ehrlich's lock and key principle is too static for many steroid-antibody complexes and that a more important factor in the binding events is the overall flexibility of these complexes. In this connection a discussion is undertaken of the properties of unsaturated steroid skeletons, the multispecificity of binding sites and further critical factors involved in the formation of the final specificity. Special attention is paid to considerations of the size of steroid determinants in connection with the question of the so-called bridge effect. The relevant expositions of this phenomenon are based in this article more on conformation changes of the steroid ligands than on direct binding interaction of the bridge substituent with the antibody. This interpretation makes it possible to interpret more broadly the experimental facts and gives new stimuli for an improvement of the present strategies of steroid immunoanalysis.

The measurement of testosterone and oestradiol-17 beta using iodinated tracers and incorporating an affinity chromatography extraction procedure

The development of sensitive radioimmunoassays (RIA) for testosterone and oestradiol-17 beta, utilising 125I-radioligands, is described. Use of an homologous bridge at the same site of attachment, for both the radioligand and the steroid-carrier protein conjugate employed in raising antibodies, normally results in a loss of assay sensitivity and precision. This was overcome in the oestradiol assay by utilising an heterologous configuration at the site of attachment (11 alpha vs 11 beta). In contrast, for testosterone, even though an homologous bridge and site of attachment was used for the radioligand and the steroid-carrier protein conjugate, a very sensitive assay with extremely high antibody titres (dilution of 1:2 X 10(6] was achieved. This finding was repeated with a different antiserum suggesting that the "bridge binding" phenomenon may be related to the position of attachment to the steroid molecule. In addition, an antibody-Sepharose 4B affinity chromatography extraction procedure has been developed for both oestradiol and testosterone. This approach allows the measurement of very low concentrations of steroids from large volumes of a variety of biological fluids. As antibody-linked Sepharose 4B uses high concentrations of antibody, steroids of similar structure are extracted from biological fluids. However, the cross-reactivity of these related steroids are very low in the RIA's, ensuring good specificity.

Radioimmunoassay of progesterone in saliva: a simplified technique using 125I-radioligand

The value of serial salivary progesterone (P) determinations for evaluation of corpus luteum function compared with sporadic serum samplings is recognized. Salivary P concentrations have previously been determined by a relatively difficult assay which utilizes a tritiated radioligand. The present study was designed to compare this conventional method with a simpler assay utilizing an iodinated radioligand. The values obtained with two different radioimmunoassay (RIA) systems were compared for samples collected throughout the luteal phase of seven normal menstrual cycles and three conception cycles. In the seven nonconception luteal phases as well as in the three conception luteal phases, daily salivary P determinations by the two techniques correlated significantly with each other (r = 0.56; P less than 0.001). For the seven nonconception luteal phases, the salivary P determinations obtained by 125I RIA (Saliva 125I) correlated significantly with the matched serum values (r = 0.54; P less than 0.001). However, the correlation was poor between the salivary P determinations obtained by the 3H RIA (Saliva 3H) and the matched serum values. The simplicity and accuracy of the 125I RIA and the convenience of saliva sampling provide a practical approach to monitor human luteal function.

A specific radioimmunoassay for androstenedione with reduced bridge-binding

Antibody used in a steroid radioimmunoassay raised against a steroid hapten-carrier protein conjugate may recognize both the hapten and the chemical bridge to the protein. Use of the same bridge in the radio-isotopic label may lead to higher affinity binding to the label than to the native steroid. Inhibition curves under these conditions are shallow and generally not acceptable for radioimmunoassay procedures. We have developed a radioimmunoassay for androstenedione that employs different bridges at the 11 beta position of the steroid for the protein conjugate and label. The resulting assay has greatly reduced bridge-binding, has an acceptable slope for the standard curve and is very specific as evidenced by low crossreactivies to other steroids.