Demonstration of type I and type II somatomedin receptors on bovine growth plate chondrocytes
The chondrocytes of the epiphyseal growth plate are the presumed target cells for hormones regulating skeletal growth. The somatomedins, a family of low molecular weight peptides, are thought to play a stimulatory role in this regulation. The cellular actions of the somatomedins are themselves determined by binding to specific receptors on target cells. Previous studies have characterized a specific receptor for somatomedin-C (Sm-C) or insulin-like growth factor I (IGF-I) on bovine growth plate chondrocytes (GPCs). We now report the characterization of a second type of somatomedin receptor on these cells that is more specific for another class of somatomedin represented by multiplication-stimulating activity (MSA) or rat insulin-like growth factor II (rIGF-II). Binding of (125I)MSA/rIGF-II to isolated GPCs was time dependent and saturable. Unlabeled Mr 7,100 MSA/rIGF-II and Sm-C/IGF-I were approximately equipotent in competing with (125I)MSA/rIGF-II for binding, while Mr 8,600 MSA/rIGF-II was an order of magnitude less potent. Low levels of competition by insulin appeared in some studies at concentrations of 10(-7) M and higher, suggesting displacement of (125I)MSA/rIGF-II binding to the Sm-C/IGF-I receptor. In affinity-labeling studies, (125I)MSA/rIGF-I labeled a complex of Mr greater than 300,000 (unreduced) and of Mr 140,000 (reduced), consistent with a type I somatomedin receptor composed of disulfide-linked subunits. (125I)MSA/rIGF-II labeled a Mr 240,000 moiety (unreduced) and Mr 260,000 (reduced), consistent with a type II somatomedin receptor. Both affinity-labeling and kinetic data revealed cross-binding of MSA/rIGF-II and insulin with the type I receptor and of Sm-C/IGF-I with the type II receptor. In contrast, the type II receptor did not recognize insulin.
- Research Organization:
- Massachusetts General Hospital, Boston (USA)
- OSTI ID:
- 6558922
- Journal Information:
- J. Orthop. Res.; (United States), Vol. 6:6
- Country of Publication:
- United States
- Language:
- English
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PEPTIDES
RECEPTORS
CHEMICAL COMPOSITION
AUTORADIOGRAPHY
BIOCHEMICAL REACTION KINETICS
CARTILAGE
CATTLE
GROWTH FACTORS
INSULIN
IODINE 125
LABELLING
SKELETON
TIME DEPENDENCE
ANIMAL TISSUES
ANIMALS
BETA DECAY RADIOISOTOPES
BODY
CONNECTIVE TISSUE
DAYS LIVING RADIOISOTOPES
DOMESTIC ANIMALS
ELECTRON CAPTURE RADIOISOTOPES
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
KINETICS
MAMMALS
MEMBRANE PROTEINS
MITOGENS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RUMINANTS
TISSUES
VERTEBRATES
550201* - Biochemistry- Tracer Techniques