Homocysteine reduces cholinesterase activity in rat and human serum

In the present study we investigated the effect of homocysteine administration, the main metabolite accumulating in homocystinuria, on cholinesterase activity in rat and human serum. For the in vivo study, 8-, 15- and 60-day-old rats received one subcutaneous injection of homocysteine (0.3, 0.4 or 0.6 μmol/g of body weight, respectively) or saline (control) and were sacrificed 1 h later, when serum was collected in order to determine cholinesterase activity. For the in vitro studies, serum of 8-, 15- and 60-day-old untreated rats or 20–25- and 52–60-day-old human beings (healthy volunteers) were incubated with 10–500 μM homocysteine. Results showed that acute hyperhomocysteinemia (in vivo study) significantly reduced cholinesterase activity in the serum of rats of all ages tested. We also observed that 500 μM homocysteine added to the incubation medium (in vitro study) significantly inhibited cholinesterase activity both in serum of rats and humans. Our findings seem to reinforce the proposed associations of cholinesterase activity with hyperhomocysteinemia.