Effects of manganese on 45Ca mobilization and contractile responses in rabbit aortic smooth muscle

1. 1. In rabbit aortic smooth muscle, 1.5 mM Mn 2+ inhibits contractile responses to norepinephrine more than those to high K +. Other associated effects include decreases in the La 3+-resistant high affinity Ca 2+ fraction, the high affinity Ca 2+ uptake component in the Scatchard-coordinate plot, and high affinity Ca 2+ uptake and binding in canine aortic microsomes. 2. 2. Higher (15 mM) concentrations of Mn 2+ are less selective. 3. 3. Thus, those Ca 2+ mobilization components and contractile responses associated with high affinity bound Ca 2+ are more sensitive to inhibition by Mn 2+.