Effect of colchicine on the ultrastructure of secretory-state smooth muscle cells from the rabbit artery wall.

Little is known about the possible role of microtubules and related structures with respect to the structural and functional heterogeneity of arterial smooth muscle cells (SMC). This study demonstrates that a short-term treatment with an antitubulin, colchicine, resulted in two major structural changes in arterial SMC in the aortic arch, the thoracic aorta and the pulmonary trunk of 20-d-old rabbits. The SMC of control rabbits showed well-developed rough endoplasmic reticulum and Golgi complexes, and numerous microtubules. Colchicine treatment affected (a) microtubules in a monotypic way (all SMC contained no microtubules after colchicine), and (b) Golgi complexes and rough endoplasmic reticulum in a pleiotypic way. In effect two major structural subpopulations of SMC were obtained; the first subpopulation displayed markedly altered Golgi complexes, whereas the rough endoplasmic reticulum was unaltered; the second subpopulation showed a vacuolar dilation of rough endoplasmic reticulum (or extensively-developed smooth sarcoplasmic reticulum), but a disappearance of Golgi complex. These data suggest that an organelle-specific sensitivity to colchicine (most likely to its antitubulin action) may contribute to the heterogeneity of SMC. They also suggest that within control SMC two subpopulations might exist which can only be detected under special conditions like colchicine treatment. The disassembly of microtubules detected in parallel may be one trigger, but not the main mechanism in the heterogeneous changes of SMC in reaction to colchicine.