Stereological studies on the epiphyseal growth plate in strontium-induced rickets. With special reference to the distribution of matrix vesicles.

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.