Fig. 2. Ribonuclease protection assay (RPA) to quantify the effect of TZ and EGF on uroplakin mRNA expression in NHU cells. NHU cells were treated in the presence or absence of TZ (1 µM) and/or EGF (5 ng/ml) for the times indicated. Total RNA was extracted and 5 µg were hybridised with ³²P-labelled human UPII, UPIb and GAPDH cDNA probes. The samples were electrophoresed and the UP bands were quantified by means of a phosphorimager and normalised against the GAPDH signal, which was used to correct for loading efficiency. Maximum uroplakin expression was taken to be 100%.