1. The effect of chronic administration of chloroquine on glucose homoeostasis was investigated in normal and diabetic rats by determining fasting plasma glucose, glycated plasma protein, plasma immunoreactive insulin, plasma protein and glycated haemoglobin. Animal weights, as well as the survival of the diabetic animals without insulin therapy, were also observed.
2. Apart from an elevation in the plasma immunoreactive insulin levels (4.1 ± 0.6 vs 2.1 ± 0.4 μg/l, P < 0.025), there were no significant differences among the other parameters compared with age-matched controls up to week 12 for the normal rats on chloroquine treatment. After 20 weeks of treatment, however, plasma glucose (7.2 ± 0.1 vs 8.4 ± 0.2 mmol/l, P < 0.005) and glycated haemoglobin (2.9 ± 0.1 vs 3.3 ± 0.1%, P < 0.01) levels were lower in the treated animals. Diabetic rats treated with chloroquine for 12 weeks before the onset of diabetes showed significantly higher plasma insulin and protein levels than control diabetic animals, while plasma glucose (17.7 ± 2.5 vs 29.4 ± 1.7 mmol/l, P < 0.005), glycated plasma protein and glycated haemoglobin (6.6 ± 0.4 vs 7.8 ± 0.4%, P < 0.05) levels were lower.
3. It is concluded that after a prolonged administration of chloroquine there is a hypoglycaemic effect in normal animals, and pretreatment with the drug ameliorates diabetes induced subsequently.