Collagen synthesis by cultured arterial smooth muscle cells during spontaneous phenotypic modulation.

Quantitative and qualitative changes in collagen synthetic activity by rabbit arterial smooth muscle cells were monitored during spontaneous phenotypic modulation from days 2-15 of culture. The cultured smooth muscle cells transformed into a synthetic phenotype, reaching a maximum of 94.6% on day 4, and then gradually returned to a contractile phenotype accounting for 59.3% on day 15 of culture. The maximum collagen synthesis was found on day 7 when the cells were in early quiescent phase and showed a 91.7% synthetic phenotype. With an increasing proportion of cells in a contractile state, total collagen synthesis per cell decreased in parallel with the reduction in total protein synthesis. Synthesis of type I collagen was predominant, and the proportion of type I + III collagen was over 85% during the entire period of culture. Synthetic activity of type IV collagen, however, was relatively increased, and reached 3.8 +/- 0.4% at day 15 in comparison with 0.8 +/- 0.1% in the late logarithmic growth phase on day 4. This significant increment of type IV collagen in vitro seems to be correlated with the phenotypic modulation of cultured smooth muscle cells into a contractile phenotype.