PASMC that attain confluence at high serum cannot maintain that cell density in low serum.

<p>Human PASMC were grown to confluence in 10% FBS and maintained in 10% serum for 7 days. Confluence was determined by light microscopy and by the demonstration of stable cell number over 7 days. Cells were then exposed to various concentrations of serum ranging from 0.1% to 10%: A) Cell counts done 7 days later. B) Cells were stained with the membrane impermeable dye ethidium homodimer-1 at different time points to determine cell viability. Ethidium homodimer-1 can only stain apoptotic or necrotic cells and is a marker of cell death. Cell death is increased by day 2 and returns to baseline by day 7. (n = 3 separate experiments, * indicates p<.05 compared with starting cell number for (A) or compared to day 0 at 10% serum for (B).