Fig 5. Effect of thrombin on stimulated B₂R phosphorylation.

Panel a: CHO/B₂ transfected cells were incubated with 1 nM BK ( -•- ) or 1 μM BK (-○-) in the presence or absence of increasing concentrations of thrombin (abscissa). The increase in [³H]AA is expressed as % on the ordinate. The effect of BK without thrombin is taken as 100 %; P < 0.05. Panel b: thrombin modified BK-induced B₂R phosphorylation in a concentration dependent manner. CHO/B₂-GFPct transfected cells untreated ( + ) or treated with 100 nM Gö6976 ( -□-) or 75 μM 2-APB(-▲-) were incubated with 1 μM BK (30 min) and increasing concentrations of thrombin (0.1 – 1 μM. BK). Data are from three separate determinations. BK increased the basal level of phosphorylation of the B₂R by 4.3 ± 0.5 fold (n=3) taken as 100%. P < 0.05 vs not-treated cells without thrombin. Thrombin in low concentrations enhanced phosphorylation of B₂-GFP by BK, higher concentrations blocked it; effects were abolished by IP₃ R and [Ca²⁺]_i release inhibitors.