Isoproterenol stimulation up-regulates the expression of MMP-7. A and B, HGC-27 and MGC-803 cells were incubated overnight in serum-free medium and then treated with 2 or 10 μM isoproterenol, respectively. The expression of MMP-7 mRNA was analyzed by RT-PCR (A) and real-time PCR (B). C, HGC-27 cells were stimulated with 0, 1 or 2 μM isoproterenol and MGC-803 cells with 0, 5 and 10 μM isoproterenol after serum starvation. The expression of MMP-7 protein was analyzed by Western blot. D, MGC-803 cells were treated with 10 μM propranolol or 1 μM ICI-118,551 for 1 h and then with 10 μM isoproterenol. MMP-7 expression was analyzed by Western blot (upper panel); the expression of β2-AR in MGC-803, MKN-45 and HGC-27 cells was detected by Western blot (lower panel).