Northern blot analysis of TIMP-1 expression. A total of 7.5 μg of total RNA was electrophoresed on 1% wt/vol agarose-formaldehyde, transfered onto nylon filters, and hybridized with TIMP-1 and GAPDH. Filters were autoradiographed at −80°C. Radiographs were scanned by an AGFA Arcus flatbed scanner.