Radioimmunoassay of antiarrhythmic peptide and its application

Summary

To establish a specific and sensitive radioimmunoassay (RIA) for antiarrhythmic peptide (AAP) and study serum AAP levels in normal Sprague-Dawley rats (NR) and spontaneous hypertension rats (SHR), AAP-bovine serum albumin (BSA) conjugate was prepared by ammonium bicarbonate method. The New Zealand rabbits were immunized by administering intradermally the conjugate. Then the rabbit anti-AAP serum was produced and iodinated AAP was made by Bolton-Hunter method. The RIA for serum AAP was set up and serum AAP levels in NR and SHR were determined. The minimal detectable range of the AAP RIA was (0.45±0.06) μg/L. The affinity constant for antiserum was 1.05×10⁹ L/mol, and the rate of cross-reactivity with atrial peptide (AP) and human growth hormone (hGH) were 0.12% and 0.20%, respectively. The mean recovery rate of high, medium and low doses was 97.6%, and the mean coefficients of variation for intra-and interbath-assay were (6.43±0.85)% and (9.62±1.04)%, respectively. The mean levels of AAP in NR with different age (3 months, 8–10 months and 18–20 months) were (1.75±0.13) μg/L, (1.74±0.11) μg/L and (1.79±0.15) μg/L, respectively, while those in SHR with different age (3 months, 8–10 months and 18–20 months) were (2.38±0.35) μg/L, (2.54±0.25) μg/L and (2.83±0.21) μg/L, respectively. The levels of serum AAP showed a positive correlation with blood pressure (r=0.8667,P<0.05). It was indicated that this AAP RIA had high specificity, high accuracy and good reproducibility. The levels of serum AAP had a close relation with blood pressure.