Effects of GSAO on protein tyrosine phosphorylation are also visible under high serum culture conditions. A PWBC were cultured in low serum (0.5% FBS) or 100% donor serum and treated with 50 μM GSAO or GSCA for 24 h where indicated. Overall, levels of protein tyrosine phosphorylation are lower in donor serum-cultured PWBC and the hyperphosphorylation of tyrosyl residues observed upon GSAO-treatment is less pronounced but still detectable. B GSAO dose-response of PWBC cultured in 100% donor serum. PWBC were treated for 24 h. GSAO-induced hyperphosphorylation on tyrosyl residues is clearly visible with 15 μM GSAO.