Agonist-induced t-PA and VWF release from cultured HUVECs.

Confluent HUVECs were pretreated with either control medium, VEGF (40 ng/mL) and ATRA (10⁻⁶ M), or sodium butyrate (NaBut; 3 mM). After 20 hours, the cells were incubated for 30 minutes in KRBH buffer with histamine (Hist; 10⁻⁵ M), forskolin (Forsk; 2 × 10⁻⁵ M), or epinephrine (Epi; 10⁻⁶ M). The latter 2 agents were added together with IBMX (I; 10⁻⁴M). The supernatants were then assayed for t-PA (panel A) and VWF (panel B) release. Results are expressed as ng/well per 30 minutes, as the mean ± SEM of at least 4 independent determinations. See text for statistical analysis.