Heterogeneity of serum peptides with immunoactivity detected by a radioimmunoassay for proinsulin-like growth factor-II E domain: description of a free E domain peptide in serum.
We have reported that normal human sera contain immunoactivity (IA) detected by a RIA directed against the first 21 amino acids of the E domain of proinsulin-like growth factor-II (pro-IGF-II). Marked elevations of E-21 IA were found in the serum of patients with nonislet cell hypoglycemia (NICTH) and patients with renal failure receiving chronic hemodialysis. In this paper we describe some of the properties of the E-21 IA of normal and abnormal sera. The E-21 IA eluted from a calibrated acid Sephadex G-50 column as two major peaks. In normal serum the first major peak had a mol wt (Mr) between 14,000-15,000, and the second peak had a Mr between 5,000-6,000. When E-21 IA from serum of a patient with NICTH was similarly studied, most of the IA was present as a Mr 11,000 peak and only a small amount was present as a 5,000-6,000 Mr peak. In contrast, most of the E-21 IA present in the sera of patients on hemodialysis was present in the smaller molecular form, which eluted from a reverse phase column as a single component. This small Mr peak lacked determinants for the IGF-II monoclonal antibody (Amano), for pooled serum IGF-binding proteins, and for the IGF-I receptors on human placental membranes. We suggest that the 15- and 11-kilodalton peaks represent the glycated and unglycated forms of pro-IGF-II (E-21) reported by others. The glycated form appears to predominate in normal serum, whereas the nonglycated form predominates in the serum of patients with NICTH and renal failure. The 5,000-6,000 Mr E-21 IA probably represents a fragment of the free E domain of pro-IGF-II. Its size is consistent with cleavage of the free E domain between Arg46 and Arg47. The accumulation of this E-21 IA in renal failure is evidence that the kidney has a major role in the clearance of this fragment, which is not accomplished by the membranes used in hemodialysis.
Daughaday
W H
WH
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Trivedi
B
B
D000368:Aged; D000911:Antibodies, Monoclonal; D002352:Carrier Proteins / Q000378:metabolism; D055598:Chemical Phenomena; D002621:Chemistry; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D000939:Epitopes; D005260:Female; D006801:Humans; D007003:Hypoglycemia / Q000097:blood; D018970:Insulin-Like Growth Factor Binding Protein 1; D007335:Insulin-Like Growth Factor II / Q000737:chemistry*; D008297:Male; D008875:Middle Aged; D010449:Peptide Mapping; D010455:Peptides / Q000097:blood / Q000737:chemistry* / Q000378:metabolism; D011498:Protein Precursors / Q000737:chemistry*; D011863:Radioimmunoassay
D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D000939:Epitopes; D018970:Insulin-Like Growth Factor Binding Protein 1; D010455:Peptides; D011498:Protein Precursors; C066038:proinsulin-like growth factor II; D007335:Insulin-Like Growth Factor II