Interaction of Tat with the endothelium. GM7373 ECs were incubated for 2 hours at 37°C or 4°C with increasing concentrations of b-Tat (A) or for the indicated periods of time with 510 nM b-Tat (B). (C) GM7373 ECs were incubated with b-Tat (510 nM) in the presence of (from left to right) heparin (0.073, 0.73, or 7.3 nM), suramin (2.1, 21, or 210 nM), or unsulfated K5 polysaccharide (7.3 nM). Alternatively, GM7373 ECs were treated with heparinase II or III (1.0, 2.5, 5.0, or 10 mU/mL) or with hyaluronidase (5.0 or 10 mU/mL) before incubation with b-Tat. Then, the amount of EC-associated b-Tat was measured. Each point is the mean ± SEM of 3 to 5 duplicate determinations.