The Effect of Chloroquine on Circulating Platelet Survival in the Rat

BACKGROUND: Chloroquine inhibits platelet aggregation. Because platelet aggregation may lead to the lysis of platelets, the effect of chloroquine administration on circulating platelet survival was studied. METHODS AND RESULTS: Platelets harvested from the blood of male inbred (WAG) rats were labeled with (111)Indium oxine and returned to other inbred rats. At timed intervals, blood samples were drawn from the rats and taken for radioactivity estimation. In some experiments, the rats (n = 10) received chloroquine (10 mg/kg) intraperitoneally daily for 3 days. Control rats (n = 10) received chloroquine (10 mg/kg) intraperitoneally daily for 3 days. Control rats (n = 10) received normal saline. Indium-labeled platelets disappeared exponentially in control and test rats. The fraction of indium disappearing/h was significantly less in chloroquine-treated rats than in control rats (0.0368 +/- 0.0016 vs 0.0520 +/- 0.0016, mean +/- SEM; P <.001). In all, 99% of the labeled platelets disappeared in 5.3 days in chloroquine-treated rats and 3.7 days in control rats. CONCLUSIONS: Chloroquine administration increases the life span of circulating platelets in rats. If the results are confirmed in humans, chloroquine may prevent the shortened platelet survival and thrombocytopenia common in malarial infection and other thrombotic disorders.