Scrutinization of the Direct Assay Method for Plasma Cyclic AMP and Clinical Applications of Nephrogenous Cyclic AMP

Publisher Website
Google Scholar
Abstract
Several problems in the measurement of plasma cyclic AMP (PcAMP) and nephrogenous cyclic AMP were studied using a YAMASA RIA Kit (YAMASA Shoyu, Choshi, Japan). In this assay method, cAMP in plasma is directly succinylated without prior deproteinization, and then it is bound to antibody in an imidazole buffer.1. So far as the blood samples were obtained with EDTA-4Na at least 5.0mM in the final concentration, PcAMP was not reduced until 16 hours after the blood samples were drawn. Even without EDTA, the reductions in PcAMP were not detected within 1 hour after the blood samples were drawn.2. This assay method for PcAMP showed parallelism in the dilution curve. Recovery was almost complete. Intra-and interassay variations were low. When plasma was incubated at 37°C for 24 hours, PcAMP became negligible. Furthermore, the values of PcAMP measured with this direct assay system almost agreed with those obtained after the purification by deproteinization and Dowex column chromatography through an anion-exchange resin. The normal values of PcAMP were 13.6 ± 3.62 pmol/ml [mean ± SD, n = 43].3. Nephrogenous cAMP expressed as a function of GFR never did show any negative values in various clinical situations. From the data of basal levels and the oral calcium tolerance test, nephrogenous cAMP appeared to be more useful than total urinary cAMP in the diagnosis of parathyroid disorders, especially hyperparathyroidism.In conclusion, the sampling of blood with EDTA is sufficient to inhibit the spontaneous decrease of cAMP in plasma. The direct assay method for PcAMP with a YAMASA RIA Kit provides qualitative and quantitative specificity, and the values determined by this assay method are comparable to those following the purification procedures. Nephrogenous cAMP, being readily measurable with this Kit, is extremely useful as an index of parathyroid function.

This publication has 0 references indexed in Scilit: