Monensin inhibition of hyaluronate synthesis in rat fibrosarcoma cells

Evidence is presented that monensin-sensitive membranes, presumably the Golgi apparatus, are involved in the synthesis of hyaluronate in rat fibrosarcoma cells. Monensin caused the inhibition of incorporation of metabolic precursors into hyaluronate produced by rat fibrosarcoma cells in a concentration- and time-dependent manner. Maximum inhibition (70-80%) was obtained on treatment with 10(-7) M monensin for 24 h. Incorporation of label into secreted hyaluronate and into that associated with the cell surface was inhibited, but incorporation into intracellular hyaluronate was not inhibited. In 3T3 cells, treatment for 24 h with 10(-7) M monensin inhibited incorporation of label only into secreted hyaluronate. The hyaluronate-rich pericellular coat, revealed by exclusion of fixed red blood cells, was depleted on treatment with monensin under the same conditions which caused inhibition of hyaluronate synthesis in the fibrosarcoma cells. Cell proliferation, as measured by DNA content/culture and [3H]thymidine incorporation, was also inhibited in a dose-dependent manner by monensin (10(-8)-10(-6) M). Protein synthesis was not inhibited at these doses, nor was monensin cytotoxic as judged by a 51Cr release assay. The inhibition of hyaluronate synthesis was independent of the antiproliferative effect of monensin because it was obtained during log phase growth or confluency and in the presence or in the absence of serum.