Influence of colchicine and vinblastine on the Golgi complex and matrix deposition in chondrocyte aggregates : An ultrastructural study

Fetal guinea-pig epiphyseal chondrocytes were isolated enzymatically, aggregated, and the aggregates maintained in organ culture. As revealed by light and electron microscopy, the cultures produced a typical cartilaginous matrix, but no calcification occurred. Exposure of aggregating cells, or preformed aggregates, to colchicine or vinblastihe at 10⁻⁵ M concentration led to disappearance of the microtubules, dissociation of the Golgi complex into single dictyosomes, and clustering of lysosomes. Thus, in treated cells the dictyosomes with accompanying vesicular structures were dispersed throughout the cytoplasm, whereas they were localized in a well-defined juxtanuclear region in control cells. The number and size of the cisternae forming a dictyosome were often reduced. Cells treated with vinblastine displayed macrotubules and an increased number of phagosomes. Both drugs reduced the deposition of intercellular matrix. In cells first exposed to either of the drugs for 2 or 5 days and then transferred to fresh medium for 3 or 6 days, the microtubules reappeared, the Golgi complex regained its normal appearance, and the amount of matrix increased. These findings are discussed in view of present concepts of the role of microtubules in cell secretion.