Organization and energy-dependent growth of microtubules in cells.

Abstract

The organization and growth of microtubules in cultured mouse macrophages and fibroblasts were examined by indirect immunofluorescence microscopy with antibodies to microtubule protein. In macrophages, microtubules converged at a small region at the cytocenter. During depolymerization and repolymerization, this region acted as a microtubule organizing center. Microtubule growth was energy-dependent, but unaffected by dibutyryl cyclic[c]AMP, cholera toxin or dibutyryl-cGMP. Fibroblasts, which did not show such a simple microtubule organization as macrophages, contained mainly 1 or 2, but occasionally as many as 4, organizing centers during repolymerization. These microtubule organizing centers often appeared as fluorescent rings with a dark center.