Fig. 8. RA induces the production of MMP-9 and uPA. (A) Effect of RA on gelatinase activity. Gelatin zymography of conditioned medium from monolayer cultures of J3B1A cells incubated with 10,100 and 1000 nM RA. The larger band of gelatin lysis corresponds to the reported molecular weight of latent MMP-9, whereas the smaller lower molecular weight band corresponds to the activated MMP-9 species. The zymogram is representative of five distinct experiments. (B) RA induces a dose- and time-dependent increase in uPA activity, as detected by casein zymography of conditioned media. (C,D) RA induces a dose-dependent increase in MMP-9 mRNA but does not modulate MT1-MMP mRNA. Confluent J3B1A cell monolayers were incubated with or without various concentrations of RA for 24 or 48 hours, after which RNA samples (5-10 µg per lane) were prepared and hybridized with either MMP-9 or MT1-MMP cRNA probes, as described in Materials and Methods. A bovine P0 ribosomal phosphoprotein cRNA probe was used to assess uniformity of loading.