The Journal of Bone and Joint Surgery, Vol 68, Issue 6 897-903, Copyright © 1986 by Journal of Bone and Joint Surgery, Inc
Localization of somatomedin-C binding to bovine growth-plate chondrocytes in situ
SB Trippel, JJ Van Wyk and HJ Mankin
The somatomedins are a family of low-molecular-weight peptides that are
thought to mediate the stimulatory effect of growth hormone on skeletal
growth. The cells that are directly responsible for skeletal growth are the
chondrocytes of the epiphyseal growth plate, and these are the presumed
skeletal target cells for somatomedin. As with other peptide growth
factors, the cellular effects of the somatomedins are initiated by the
interaction of the growth factor with specific receptors on target-cell
surface membranes. Chondrocytes that have been isolated from bovine growth
plates were previously found to possess specific surface receptors for the
principal growth-hormone-dependent somatomedin, somatomedin-C. These
studies indicated that the interaction of growth-plate chondrocytes with
somatomedin-C involves specific receptor-binding followed by somatomedin-C
internalization by the cell, a process identical to that identified in the
mechanism of action of other peptide growth factors in other cells. These
studies, however, left unanswered the questions of whether there are
differences in binding of somatomedin-C by the different cell populations
within the physis and whether somatomedin-C has access to cells in intact
tissues. The current studies address these issues and indicate that bovine
physeal chondrocytes in situ are accessible to exogenous somatomedin-C,
that they specifically bind somatomedin-C in situ, and that cells of
different physeal zones bind somatomedin-C differently. Labeled
somatomedin-C is specifically bound by cells of all physeal zones. However,
the binding is greatest for those cells undergoing active synthesis of DNA
in the proliferative zone.(ABSTRACT TRUNCATED AT 250 WORDS)