uPA induction by MNNG treatment.

(A) Analysis of uPA mRNA expression in MNNG-stimulated C2C12 (top) and NIH3T3 (bottom) cells. Cells were cultured in 0.5% FBS for 16 hours and then treated with MNNG (70 μmol/L). Total RNA was extracted at the indicated time points (in hours) after MNNG stimulation and analyzed by Northern blotting using the mouse uPA and GAPDH cDNA probes as indicated. (B) Effect of RNA and protein synthesis inhibitors on MNNG-stimulated uPA expression. C2C12 cells were treated for 2 hours with MNNG as in (A), except that cultures were grown in the presence (+) or absence (−) of actinomycin D (5 μg/mL) or cycloheximide (10 μg/mL), which were added 30 minutes before the addition of MNNG.