Biomaterial Database

Vascular smooth muscle cells synthesize two forms of insulin-like growth factor binding proteins which are regulated differently by the insulin-like growth factors. 1993

W S Cohick, and A Gockerman, and D R Clemmons

Department of Medicine, University of North Carolina School of Medicine, Chapel Hill 27599.

Vascular smooth muscle cells (SMC) synthesize insulin-like growth factor-I (IGF-I), which is a mitogen for this cell type in vitro. Since IGF binding proteins (IGFBP) modulate IGF bioactivity, we determined which IGFBPs were secreted by porcine SMC. Porcine SMC secreted 34,000 and 24,000 M(r) forms of IGFBPs which were identified as IGFBP-2 and IGFBP-4, respectively, by immunoblotting. Northern blot analysis showed single transcripts of 1.6 kb and 2.4 kb for IGFBP-2 and IGFBP-4, respectively. Secretion of IGFBP-2 was not regulated to a significant degree, with insulin, IGF-II, IGF-I, forskolin, and dibutyryl cyclic adenosine monophosphate (cAMP) inducing minimal changes in IGFBP-2 secretion of less than 30% by radioimmunoassay (RIA). Insulin increased (2.8 +/- 0.1-fold) the abundance of IGFBP-4 protein in conditioned media (CM) and increased IGFBP-4 mRNA levels. Growth factors for SMC such as platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), and transforming growth factor beta-1 (TGF beta-1) were without effect on either IGFBP-2 or -4. IGF-I treatment decreased the amount of IGFBP-4 present in CM, but a corresponding decrease in IGFBP-4 mRNA levels was not observed. In order to determine if IGFBP-4 could modulate IGF-I bioactivity, IGFBP-4 was added to pSMCs with and without IGF-I. IGF-I alone (20 ng/ml) induced a 1.6 to threefold increase in 3H-thymidine incorporation. Addition of IGFBP-4 (between 50 and 250 ng/ml) to cultures containing IGF-I (20 ng/ml) had no effect on DNA synthesis compared to that observed with IGF-I alone, while 500 ng/ml consistently caused a small decrease (15 +/- 5%; mean +/- SE). Immunoblotting of the CM obtained at the end of the 3H-thymidine assay showed a loss of intact IGFBP-4 in the cultures containing IGF-I. This corresponded with an increase in the abundance of a 16,000 M(r) immunoreactive fragment that did not bind IGF-I. Coincubation with insulin had no effect on the amount of IGFBP-4 that was converted to fragment, suggesting that the reaction was dependent upon IGF-I binding to IGFBP-4. In contrast, addition of IGFBP-4 (500 ng/ml) to human fibroblast cultures with IGF-I (20 ng/ml) almost completely inhibited the stimulatory effect of IGF-I on DNA synthesis and no increase in fragment was detected in the CM. In summary, SMC secrete IGFBP-2 and IGFBP-4, both of which have been shown to regulate IGF-mediated DNA synthesis.(ABSTRACT TRUNCATED AT 400 WORDS)

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
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D009131	Muscle, Smooth, Vascular	The nonstriated involuntary muscle tissue of blood vessels.	Vascular Smooth Muscle,Muscle, Vascular Smooth,Muscles, Vascular Smooth,Smooth Muscle, Vascular,Smooth Muscles, Vascular,Vascular Smooth Muscles
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
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012333	RNA, Messenger	RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.	Messenger RNA,Messenger RNA, Polyadenylated,Poly(A) Tail,Poly(A)+ RNA,Poly(A)+ mRNA,RNA, Messenger, Polyadenylated,RNA, Polyadenylated,mRNA,mRNA, Non-Polyadenylated,mRNA, Polyadenylated,Non-Polyadenylated mRNA,Poly(A) RNA,Polyadenylated mRNA,Non Polyadenylated mRNA,Polyadenylated Messenger RNA,Polyadenylated RNA,RNA, Polyadenylated Messenger,mRNA, Non Polyadenylated
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
D015151	Immunoblotting	Immunologic method used for detecting or quantifying immunoreactive substances. The substance is identified by first immobilizing it by blotting onto a membrane and then tagging it with labeled antibodies.	Dot Immunoblotting,Electroimmunoblotting,Immunoelectroblotting,Reverse Immunoblotting,Immunoblotting, Dot,Immunoblotting, Reverse,Dot Immunoblottings,Electroimmunoblottings,Immunoblottings,Immunoblottings, Dot,Immunoblottings, Reverse,Immunoelectroblottings,Reverse Immunoblottings