Fig. 10.

The secretagogue-stimulated increase in calcium-dependent SP-A binding is attenuated by Ab directed against P63 protein. Type II cells were placed on Transwell membranes and incubated for 24 h in HBSS without or with calcium (1 mM). Anti-P63 or nonimmune IgG was added for 15 min followed by the addition of ¹²⁵I-SP-A (0.5 μg/ml) for 1 h at 4°C. The cells were harvested, and the calcium-dependent binding was determined by subtracting the binding in the absence of calcium (calcium-independent) from the total binding with calcium. Data are the means ± SE of 3–9 experiments performed in triplicate expressed as percentage of the calcium-dependent binding (20.5 ± 0.8 ng ¹²⁵I-SP-A/mg cell protein, n = 9), which was set equal to 100% (Control, no cAMP). *Statistically significant difference from binding without additions or with IgG. P < 0.05.