Inhibition of erythrocyte and plasma cholinesterase by 5-hydroxytryptamine

The inhibition of human erythrocytes and plasma cholinesterase (ChE) by 5-hydroxytryptamine in vitro was studied. Constants characterising this inhibition, namely the inhibition rate for red blood cells RBCs (2.5 x 10(4) (mol/l)-1 min-1) and plasma ChE (1.08 x 10(4) (mol/l)-1 min-1) as well as the rate constant for spontaneous reactivation for RBCs (0.3 min-1) and plasma ChE (0.26 min-1) were calculated. The inhibition of RBCs and plasma ChE by 5-hydroxy-tryptamine was found to be of the competitive type.