The Journal of Bone and Joint Surgery, Vol 64, Issue 1 32-38, Copyright © 1982 by Journal of Bone and Joint Surgery, Inc
The measurement of proteoglycan in the mineralizing region of the rat growth plate
N Mitchell, N Shepard and J Harrod
Using a recently developed technique for measuring proteoglycan by x-ray
microprobe analysis, we examined six-week-old rat growth plates. In the
proliferating zone, the proteoglycan concentration was found to be
relatively low in the transverse septa, but somewhat higher in the
longitudinal septa between the proliferating chondrocytes. In the lower
hypertropic zone, in the region of the degenerating hypertrophic
chondrocytes, the immediate pericellular area had a very high concentration
of proteoglycan, as was obtained. These results indicate that either
proteoglycan concentrations fall to very low levels in fully mineralized
cartilage, or that the mineralization of cartilage interferes in some way
with the measurement of microprobe signals from proteoglycans. We speculate
that high levels of proteoglycan are necessary for mineralization in the
epiphysis of the rat. Clinical Relevance: The spot-to-spot analysis of
proteoglycan by microprobe demonstrates the usefulness of this tool in
analyzing minute volumes of cartilage for proteoglycan. It further
demonstrates that mineralization of growth-plate cartilage is associated
with changing patterns of concentration of proteoglycan. These normal
patterns may constitute a basis for comparison in similarly evaluating
concentrations of proteoglycan in diseases of growth disturbance.
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