p110γ is functionally expressed in venular endothelium. (A) Immunoblots of the p110γ catalytic subunit using recombinant proteins (i) and lysates obtained from HUVECs or neutrophils (ii), or the murine endothelioma cell line bEND3.1 (iii). Measurement of (B) PI3Kγ and (C) PI3Kδ kinase activity. Immunoprecipitates of p110γ and p110δ (▪) from HUVEC lysates were assayed for PI3K activity with or without the addition of 10 μM IC87114 or LY294002 as described in “Materials and methods.” ▪ indicates control. The results are expressed as the percent of activity in untreated immunoprecipitates and represent the mean plus or minus SD values of 3 independent determinations in duplicate. *P < .01 as compared with untreated cells.