Inhibition of Access of Bound Somatomedin to Membrane Receptor and Immunobinding Sites: A Comparison of Radioreceptor and Radioimmunoassay of Somatomedin in Native and Acid-Ethanol-Extracted Serum

摘要: No agreement exists concerning the necessity for extracting serum somatomedin (Sm) before radioreceptor assay (RRA) and RIA. We have developed a simplified system of Sm extraction which has permitted quantitative comparison native extracted Sm. To 0.8 ml mixture 87.5% ethanol 12.5% 2 N HC1, 0.2 is added. After centrifugation, 0.5 supernatant neutralized with 0.855 M Tris base (XT). Recovery added 125I-labeled insulin-like growth factor I ([125I]IGF-I) was nearly quantitative. Neutral gel filtration studies established that virtually all binding complex removed by acid-ethanol precipitation. The addition 100 µl Tris-neutralized buffer (AE B) to [125I]IGF-I human placental membrane RRA produced an insignificant shift in displacement curve partially purified IGF reference preparation; [125I]Sm C RIA greater but did not prevent accurate measurement when AE B blank stan...