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Figure 1 Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) zymography of media conditioned by human monocyte-derived macrophages after 24-h exposure to nitroglycerin (NTG). (a) Cells were exposed for 24 h to glycerol 200 pmol (Lanes 1 and 2) or NTG 200 pmol (Lanes 3 and 4). Aliquots of conditioned media, normalized to 15 µg total protein, were run on SDS-PAGE (10%[w/v] gel) supplemented with 1 mg/ml gelatin substrate under nonreducing conditions. Zones of clearing at approximately 90 kDa (as measured by simultaneous electrophoresis of protein standards, Lane 5) indicate gelatinolytic activity of both latent (heavier) and active (lighter) matrix metalloproteinase (MMP)-9. Band densities are: Lanes 1 and 2, glycerol (latent 162,160; 167,492: active 176,945; 173,336) and Lanes 3 and 4, NTG 200 pmol (latent 29,515; 22,223: active 39,664; 31,960). (b) Aliquots of conditioned media, normalized to 15 µg total protein, were treated with 1 mM p-aminophenyl mercuric acetate (APMA) for 30 min at 37°C. Treated samples were then run on SDS-PAGE (10%[w/v] gel) supplemented with 1 mg/ml gelatin substrate under nonreducing conditions. Zones of clearing at approximately 90 kDa (as measured by simultaneous electrophoresis of protein standards, Lane 5) indicate gelatinolytic activity of both latent and active MMP-9. Band densities are Lanes 1 and 2, glycerol (active 269,957; 276,765) and Lanes 3 and 4, NTG 200 pmol (active 321,321; 302,633). MW = molecular weight.