Time dependence of the effect of rhIL-6 on plasminogen mRNA expression in Hep3B cells. (A) Hep3B cells were grown in serum-free EMEM supplemented with 0.1% BSA for 24 hours, followed by culture in the presence of 500 U/mL rhIL-6 in serum free EMEM containing 0.1% BSA for the indicated times and total RNA was prepared. The lane marked 0 represents mRNA from cells cultured in the absence of rhIL-6 for 48 hours. Northern blot analysis was performed using a ³²P-cDNA human plasminogen fragment and the ³²P-cDNA murine cyclophilin fragment. Migration of RNA molecular size standards is shown on the left. (B) Fold-stimulation of plasminogen mRNA level was determined as the ratio of plasminogen/cyclophilin hybridization band intensity as determined by laser densitometry. The ratio was normalized to one for untreated cells.