Hypoxia induces expression of SCF and FGF-2 in vitro. Cerebral cortical cultures were exposed to hypoxia for up to 24 hours, and cellular expression of growth factors and cytokines was measured by Western blotting (a), which showed increased expression of SCF and FGF-2 at 4–24 hours. SCF expression was quantified by computer densitometry (b). SCF levels were also increased after the indicated periods of hypoxia (h) in culture supernatants (c). Enhanced expression of SCF and FGF-2 was due to transcriptional activation, because RT-PCR showed increases in SCF and FGF-2 mRNA levels (d). Data are representative blots from three experiments (a, c, d) or mean ± SEM, n = 3 (b).