Hypoxia selectively upregulates IL-8 mRNA expression. Macrophages were exposed to normoxia (N), hypoxia (H) or LPS (1 µg/ml) for 2 hours and RNase protection assay performed with multiple RNA riboprobes (see methods). IL-8 is the only mRNA species to be upregulated by hypoxia. RANTES*, IP-10*, MIP-1β, MIP-1α and MCP-1 were all downregulated by hypoxia (P < 0.02) (11A). In contrast, LPS significantly upregulated the majority of chemokines (P < 0.02) (11B). A representative gel is shown (11C). For clarity the probe template is not shown. (*Expression of RANTES and IP-10 was comparatively low. Prolonged radiographic exposure for 3 days however revealed a clear normoxic RANTES and IP-10 bands and reduced expression under hypoxic conditions.) Hypoxia inhibited TNF-α expression (P < 0.05) and LPS significantly increased expression (P < 0.02) (12A). A representative gel is shown (12B).