Fig. 10.
Decreased basal rates of smooth muscle cell apoptosis in the chronically inflamed intestine are dependent on IGF-I and αvβ3 integrin. Basal rates of smooth muscle cell apoptosis are decreased in the TNBS-treated, chronically inflamed rat colonic smooth muscle (solid bars) compared with vehicle-treated uninflamed colonic muscle (open bars). In the presence of either the αvβ3 integrin inhibitor echistatin (100 nM) or the IGF-I receptor tyrosine kinase inhibitor AG1024 (10 μM), basal rates of apoptosis were increased, implying that activation of αvβ3 integrin and the IGF-I receptor by endogenous ligands regulate apoptosis in both the uninflamed and chronically inflamed intestine. The levels of nucleosomes were quantified by ELISA and were used as a measure of apoptosis. Results are expressed as relative A405. *P < 0.05 vs. apoptosis in vehicle-treated colonic muscle cells; **P < 0.05 vs. apoptosis in colonic muscle cells isolated from control vehicle-treated rats. ***P < 0.05 vs. apoptosis in colonic muscle cells isolated from control TNBS-treated rats.