Rings were incubated with Krebs containing normal glucose (NG, 6 mM), or Krebs containing MnTMPyP (25 μM) for 20 min or Krebs containing MnTMPyP and high glucose (HG, 46mM) for 3 h (A) or MnTMPyP and PMA (0.1 μM) for 3 h (B) before concentration response curve (CRC) to ACh was determined. Data are presented as the mean ± S.E.M. Pretreatment of aorta with MnTMPyP prior to HG or PMA partially but significantly improved altered ACh responses in HG or PMA (#P < 0.05 vs ACh CRCs in HG or PMA (dotted lines), unpaired t-test). However, prior treatment with MnTMPyP did not fully restore ACh responses in HG or PMA (*P < 0.05 vs 2nd CRC in NG, paired t-test).