Untitled

Abstract

A recently developed radioreceptor assay (RRA) (1) that employs 3H-naloxone and rat brain membrane homogenates was improved two ways. First, the brain membranes were preincubated in the presence of sodium ions, and second, manganase-II ions were added to the sample incubations. These changes enhanced the assay sensitivity and reproducibility with stored membrane preparations and reduced the effects of serum constituents (Na+) on ligand-receptor binding. Patient sera were assayed by radioimmunoassay (RIA) and RRA after fentanyl administration and by high-performance liquid chromatography (HPLC) and RRA after morphine administration. The results with both fentanyl assays were comparable, and no fentanyl metabolites were detectable by RRA after HPLC of serum extracts. In contrast, preliminary results with the HPLC-RRA procedure suggest the presence of an active morphine metabolite of unknown structure in sera obtained from patients on morphine therapy.

Development and validation of a radioreceptor assay for the determination of morphine and its active metabolites in serum

“…Especially, sodium, which is present during this assay in a final concentration of 7 mM, is known to reduce the binding affinity of -opioid agonists, while increasing the binding affinity of -opioid antagonists [25,48]. The opposite is true for divalent cations, like manganese, which can counteract the effects of sodium, as discussed by Levi et al [25]. Also magnesium is known for its positive effect on the agonist affinity state of the receptor [49].…”

“…The QC-samples were back-calculated from the calibration curve using Eq. (1) [25,38]. The IC 50 -value was converted via the Cheng-Prusoff equation (Eq.…”

“…While radioreceptor assays have been developed for other opiate narcotics like morphine and fentanyl [22][23][24][25][26][27], this is not the case for the important metabolite morphine-6-␤-glucuronide. M6G has only been determined in biological samples using liquid chromatography [28][29][30][31][32][33] and as morphine equivalents with immunoassays [20,34].…”

Receptor–ligand binding assays: Technologies and Applications

“…The effect of incubation time, temperature, pH and ionic strength on the affinity of the ligand for its receptor and on receptor stability need to be assessed. Especially the presence of sodium can be detrimental for agonist binding affinity in some receptors [171][172][173]. The second aspect is the choice of a suitable receptor preparation.…”

Construction and Performance Characteristics of New Fentanyl-Selective Plastic Membrane Electrode

“…Illicit use of pharmaceutical fentanyls first appeared in the mid-1970s in the medical community and continues to be a problem in the United States of America. Therefore, various methods have been developed for its quantitative determination: e.g., radioimmunoassay, [1][2][3][4][5]11,16,28 radioreceptor assay, [6][7][8] enzyme-linked immunosorbent assay, [9][10][11][12][13] fluoroimmunoassay, 14 gas chromatography, [15][16][17][18][19][20] capillary gas chromatography, [21][22][23] gas chromatography-mass spectrometry, 4,21,[24][25][26][27][28] thin-layer chromatography, 26 gas liquid chromatography, 29 high-performance liquid chromatography, [30][31][32][33][34][35][36]38 micellar electrokinetic capillary chromatography, 37 and electroencephalography, 38 etc., all with the disadvantage of tedious sample preparation.…”