Biomaterial Database

Immunoreactive somatomedin-C/insulin-like growth factor I and its binding protein in human milk. 1984

R C Baxter, and Z Zaltsman, and J R Turtle

Milk contains cell growth factors, but somatomedin-C/insulin-like growth factor I has not previously been identified. Acid-ethanol extracts of fresh human milk samples displaced somatomedin-C tracer from the specific somatomedin-C antiserum Tr4 parallel to standard. In samples obtained between days 1 and 9 postpartum, highest levels [17.6 +/- 10.4 (+/- SD) ng/ml; n = 7) were found in day 1 samples; these fell to stable levels of 6-8 ng/ml over the next several days. Sephadex G-200 chromatography of fresh 1- to 2-day-postpartum milk samples revealed immunoreactive peaks of approximately 150,000 and 40,000 mol wt, accounting for about 80% of the immunoreactivity; the remainder corresponded in elution volume to free somatomedin-C. On chromatography of the high molecular weight fractions in 1 M acetic acid, most of the immunoreactivity shifted to the position of somatomedin-C. Milk samples stripped of their endogenous somatomedins by ion exchange chromatography at low pH specifically bound somatomedin-C tracer in proportion to the amount of added protein up to 20% binding. Displacement of tracer by unlabeled somatomedin-C indicated an association constant of about 1 X 10(10) liter/mol. Fresh milk incubated with somatomedin-C tracer and fractionated by neutral gel chromatography bound the tracer predominantly in the 40,000 mol wt region, which was abolished when excess unlabeled peptide was included in the incubation. These results indicate that fresh human milk contains immunoreactive somatomedin-C, of which a significant proportion is not protein bound at neutral pH. Somatomedin-C may account for some of the mitogenic activity of milk reported by others. The role of this activity in neonatal growth is unknown.

UI	MeSH Term	Description	Entries
D007328	Insulin	A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1).	Iletin,Insulin A Chain,Insulin B Chain,Insulin, Regular,Novolin,Sodium Insulin,Soluble Insulin,Chain, Insulin B,Insulin, Sodium,Insulin, Soluble,Regular Insulin
D007334	Insulin-Like Growth Factor I	A well-characterized basic peptide believed to be secreted by the liver and to circulate in the blood. It has growth-regulating, insulin-like, and mitogenic activities. This growth factor has a major, but not absolute, dependence on GROWTH HORMONE. It is believed to be mainly active in adults in contrast to INSULIN-LIKE GROWTH FACTOR II, which is a major fetal growth factor.	IGF-I,Somatomedin C,IGF-1,IGF-I-SmC,Insulin Like Growth Factor I,Insulin-Like Somatomedin Peptide I,Insulin Like Somatomedin Peptide I
D008895	Milk, Human	Milk that is produced by HUMAN MAMMARY GLANDS.	Breast Milk,Human Milk,Milk, Breast
D010455	Peptides	Members of the class of compounds composed of AMINO ACIDS joined together by peptide bonds between adjacent amino acids into linear, branched or cyclical structures. OLIGOPEPTIDES are composed of approximately 2-12 amino acids. Polypeptides are composed of approximately 13 or more amino acids. PROTEINS are considered to be larger versions of peptides that can form into complex structures such as ENZYMES and RECEPTORS.	Peptide,Polypeptide,Polypeptides
D011863	Radioimmunoassay	Classic quantitative assay for detection of antigen-antibody reactions using a radioactively labeled substance (radioligand) either directly or indirectly to measure the binding of the unlabeled substance to a specific antibody or other receptor system. Non-immunogenic substances (e.g., haptens) can be measured if coupled to larger carrier proteins (e.g., bovine gamma-globulin or human serum albumin) capable of inducing antibody formation.	Radioimmunoassays
D002352	Carrier Proteins	Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes.	Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D002850	Chromatography, Gel	Chromatography on non-ionic gels without regard to the mechanism of solute discrimination.	Chromatography, Exclusion,Chromatography, Gel Permeation,Chromatography, Molecular Sieve,Gel Filtration,Gel Filtration Chromatography,Chromatography, Size Exclusion,Exclusion Chromatography,Gel Chromatography,Gel Permeation Chromatography,Molecular Sieve Chromatography,Chromatography, Gel Filtration,Exclusion Chromatography, Size,Filtration Chromatography, Gel,Filtration, Gel,Sieve Chromatography, Molecular,Size Exclusion Chromatography
D005260	Female		Females
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D013002	Somatomedins	Insulin-like polypeptides made by the liver and some fibroblasts and released into the blood when stimulated by SOMATOTROPIN. They cause sulfate incorporation into collagen, RNA, and DNA synthesis, which are prerequisites to cell division and growth of the organism.	Sulfation Factor,Somatomedin,Factor, Sulfation