Time dependence of the effect of rhIL-6 on plasminogen mRNA expression in primary murine hepatocytes. (A) Primary murine hepatocytes were isolated as described in Materials and Methods. The cells were grown in serum free EMEM supplemented with 0.1% BSA for 24 hours, followed by incubation with 500 U/mL rhIL-6 for the indicated times in the serum free EMEM plus 0.1% BSA. Total RNA was isolated and Northern blot analysis was performed as described in Materials and Methods using ³²P-cDNA probes for murine plasminogen and for murine cyclophilin. Migration of RNA molecular size standards is shown on the left side of the panel. (B) Fold-stimulation of plasminogen mRNA levels was determined as the ratio of plasminogen/cyclophilin hybridization band intensity determined by laser densitometric scanning of the autoradiogram in (A). The ratio was normalized to one for untreated cells.