Objective To examine the expression of matrix metalloproteinase-9 (MMP-9) in human bronchial epithelial cells treated with calcitonin - gene - related peptide (CGRP). Methods RT-PCR and gelatin zymography were performed to examine the dynamic expression and activity of MMP-9 in human bronchial epithelial cells at different doses (10-10, 10-9, 10-8, 10 -7, and 10-6 mol/L) and different time points (6, 12, 18, 24, 36, and 48 h) after the stimulation of CGRP. Results The unstimulated human bronchial epithelial cells only secreted a small amount of MMP-9. After the CGRP stimulation, the expression...