A Sensitive Radioimmunoassay for Somatomedin-C/Insulin-Like Growth-Factor I Based on Synthetic Insulin-Like Growth Factor 57-70

Abstract

We have developed a region-specific radioimmunoassay for somatomedin-C/insulin-like growth factor-I (IGF-I) directed against IGF-I 57-70. This sequence includes part of the A region and all of the carboxyterminal D region. In addition to being highly specific, this immunoassay is sensitive to as little as 1 ng/ml of IGF-I, and has half-maximum displacement by 10 ng/ml of IGF-I. Comparison to other existent immunoassays for IGF-I shows correlation coefficients of greater than 0.95. This immunoassay has the advantage of being directed against a known region of the IGF-I molecule which is on the exterior of the 3-dimensional structure, and can use a readily available synthetic peptide as both radioligand and standard.

Serum Insulin-Like Growth Factor 1 and the Risk of Ischemic Stroke

“…At the baseline examination, 3 mL of serum from each participant was obtained from subjects in a supine, non-fasting state in the afternoon and stored at -80° C. Serum IGF-1 was measured by radioimmunoassay after acid-ethanol extraction in 3 batches (16); the intra-assay coefficient of variation was less than 4%. Insulin-like growth factor binding protein (IGFBP) levels were not measured.…”

Insulin‐Like Growth Factor‐1 and Interleukin 6 Predict Sarcopenia in Very Old Community‐Living Men and Women: The Framingham Heart Study

“…Mean time between drawing and PBMC isolation was 75 (range 35–120) minutes. For measurement of IGF‐1, serum was shipped on dry ice to Endocrine Sciences (Calabasas Hills, CA) for three batched measurements, using radioimmunoassay after acid ethanol extraction 33 . No binding proteins were measured.…”

Association of Insulin‐Like Growth Factor‐I with Body Composition, Weight History, and Past Health Behaviors in the Very Old: The Framingham Heart Study

“…Serum was shipped on dry ice to Endocrine Sciences (Calabasas Hills, CA) for three batched measurements. IGF‐I was measured by radioimmunoassay after acid ethanol extraction 15 . No binding proteins were measured.…”