Applying stereological principles, we recently demonstrated a
matrix-vesicle distribution between the zones of the epiphyseal growth
plate that is at variance with the generally accepted distribution. In the
present study of strontium-induced rickets we demonstrated a similar
bimodal distribution, the highest matrix-vesicle volume fraction being
found in the resting and hypertrophic zones and the lowest, in the
proliferative zone. These volume-fraction differences are due to
differences in the number of vesicles between zones, the variation in mean
diameter being rather small. The disturbed mineralization in
strontium-induced rickets is associated with a diminished reduction of the
matrix-vesicle volume fraction in the lower part of the growth plate
compared with normal animals. The findings may indicate that matrix-vesicle
removal is a part of the mineralization process, but a causal connection
cannot be proved on the basis of our results. Our findings are, however,
compatible with the earlier-posed cell-debris theory for matrix-vesicle
origin and distribution.