z-logo
Premium
Cell density‐dependent decrease in cytoskeletal actin and myosin in cultured osteoblastic cells: Correlation with cyclic AMP changes
Author(s) -
Egan John J.,
Gronowicz Gloria,
Rodan Gideon A.
Publication year - 1991
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.240450116
Subject(s) - cytoskeleton , myosin , actin , microfilament , cytochalasin d , microbiology and biotechnology , chemistry , biophysics , osteoblast , intracellular , biology , cell , biochemistry , in vitro
During bone development, osteoblasts form a contiguous layer along recently deposited osteoid and their morphology changes from fibroblast‐like to cuboidal. In culture, similar changes occur with increased cell density. We examined the possible role of cyclic AMP in this process since cyclic AMP was reported to increase in fibroblasts with increased cell density and similar shape changes were seen in response to parathyroid hormone, which also increases cellular cyclic AMP in osteoblastic cells. Osteoblast‐enriched rat calvaria cells were seeded at increasing density. The distribution between Triton X‐100 extractable and nonextractable actin and myosin was estimated by polyacrylamide gel electrophoresis. Intracellular cyclic AMP was estimated by prelabeling the cellular ATP pool with 3 H‐adenine, followed by extraction and separation of 3 H‐cAMP by high‐performance liquid chromatography. We found that osteoblastic cells contain about 40 pg actin and 5.3 pg myosin per cell. Around 60% of the actin and 70% of the myosin were in the nonextractable (crosslinked) form at cell densities of 10,000 to 50,000 cells per cm 2 . Above 50,000 cells/cm 2 , there was a cell density‐dependent reduction in crosslinked actin and myosin and a concomitant increase in cellular cyclic AMP. A comparable rise in cyclic AMP, produced by incubation with phosphodiesterase inhibitors, and treatment with other agents that increase cyclic AMP produced a similar decrease in the level of cytoskeletal actin and myosin. Cytochalasin B treatment, through its effect on actin polymerization, produced similar changes in cell shape and cytoskeletal actin. The findings suggest that an elevation in intracellular cyclic AMP may play a role in the density‐dependent changes in cell shape and microfilament organization observed in osteoblasts.

This content is not available in your region!

Continue researching here.

Having issues? You can contact us here