Effects of hypoxia and other injurious stimuli on collagen secretion and intracellular growth stimulating activity of bovine aortic smooth muscle cells in culture.

Bovine arterial smooth muscle cells in culture were incubated in hypoxia and total cellular DNA and collagen secretion during and after the hypoxic period was measured as well as the effect of conditioned medium from hypoxic cells on these parameters. Collagen secretion decreased by 16.4% compared to controls during hypoxia but was increased by 41.4% in the post-hypoxic period. Total cellular DNA was significantly lower after both periods. New cultures, receiving conditioned medium from hypoxic cultures, showed an increased collagen secretion by 32.2% compared to controls while total cellular DNA was not changed. Growth stimulating activity, previously shown to be released from lysed cultured SMC, was assayed by exposing SMC cultures to supernatant from lysed cells that had been incubated in hypoxia or exposed to other potential atherogenic stimuli. The growth stimulating activity per cell could be increased by incubating cells in hypoxia, or exposing them to low density lipoproteins or cigarette smoke condensate in concentrations high enough to cause a decrease in cell number. It was suggested that the described effects might contribute to increased cell proliferation and collagen formation in the development of atherosclerosis.