EFFECT OF STRETCH ON GROWTH AND COLLAGEN-SYNTHESIS IN CULTURED RAT AND LAMB PULMONARY ARTERIAL SMOOTH-MUSCLE CELLS

There are no studies of the effect of stretch in cultured pulmonary va scular smooth muscle, and some data suggest that a stretch-mediated in crease in connective tissue synthesis in pulmonary arteries is mediate d by the endothelium. To investigate whether stretch can serve as a gr owth stimulus in this smooth muscle, we studied two types of cultured pulmonary arterial smooth muscle cells (a multiply passaged clonal lin e of rat cells [PAC1], and early passage lamb cells [EPTC]). Cells wer e grown on a collagen-coated silicone surface and subjected to repetit ive stretch (0.33-0.5 Hz; 10-20% strain). The relative rates of total RNA, DNA, protein, and soluble collagen synthesis were determined usin g H-3 precursors, and c-fos and collagen mRNAs by Northern blot analys is. Stretch caused no significant change in the rate of RNA synthesis in either PAC1 cells (+9%) or EPTC (-3%). The relative rate of total p rotein synthesis was decreased by stretch (6% in PAC1 cells and 36% in EPTC [both NS]) as was the rate of collagen synthesis (-24% in EPTC [ NS]). In EPTC, the percentage of H-3-thymidine labeled cells was modes tly increased with 24 h stretch (17 +/- 5.7%; P < .001), but trichloro acetic acid (TCA) precipitated H-3-thymidine was unaltered by stretch, and the number of cells not significantly changed with stretch. c-fos mRNA expression was only inconsistently induced by stretch x 30 min i n EPTC, and not at all in PAC1 cells. Expression of mRNA for alpha1 (I ) and alpha1 (III) collagen was not changed significantly by 24 h or 4 8 h of stretch. We conclude that stretch does not serve as a significa nt growth stimulus in cultured pulmonary vascular smooth muscle cells in this system. These findings do not rule out the possibility that st retch is a growth stimulus for these cells under different conditions, but do suggest that other models will be needed to determine if and h ow mechanical stimuli affect growth of pulmonary vascular smooth muscl e. (C) 1993 Wiley-Liss, Inc.