Fig. 4.

Phosphatidylinositol 3-kinase (PI3-kinase) inhibitors block the biological activity of SP-A on PC liposome uptake. A: LY-294002. Type II cells plated on Transwell membranes were incubated without LY-294002 (No LY294002) or with LY-294002 (10 μM) for 15 min, with or without cAMP (0.1 mM) for 1 h. ³H-DPPC-labeled liposomes (45 μg PC/ml) were added without (Liposomes) or with SP-A at 5 μg/ml (Liposomes + SP-A) for 2 h. The cells were harvested with trypsin. Data are means ± SE of duplicate dishes in 3 experiments. a, Significant difference from liposomes alone, no additions; b, significant difference from Liposomes + SP-A, no cAMP (None); c, significant difference from no LY-294002. P < 0.05; n = 3. B: wortmannin. Type II cells plated on Transwell membranes were incubated without wortmannin or with wortmannin (50–300 nM) for 15 min, with or without cAMP (0.1 mM) for 1 h. ³H-DPPC-labeled liposomes (45 μg PC/ml) were added without SP-A (Control, no cAMP and no SP-A added to liposomes) or with SP-A at 5 μg/ml (cAMP and SP-A with liposomes) for 2 h. The cells were harvested with trypsin. Data are means ± SE or means ± range of duplicate or triplicate dishes in 2 (Control, wortmannin at 50 nM) to 5 experiments. *Significant difference from Control; #significant difference from cAMP + SP-A, no wortmannin, P < 0.05, n = 3–5.