Background and Purpose
: A water decoction of the poisonous shrub Cleistanthus collinus
is used for suicidal purposes. The mortality rate is 28%. The clinical profile includes distal renal tubular acidosis (DRTA) and respiratory failure. The mechanism of toxicity is unclear.
: To demonstrate features of C. collinus
toxicity in a rat model and to identify its mechanism(s) of action.
Materials and Methods
: Rats were anesthetized and the carotid artery was cannulated. Electrocardiogram and respiratory movements were recorded. Either aqueous extract of C. collinus
or control solution was administered intraperitoneally. Serial measurements of blood gases, electrolytes and urinary pH were made. Isolated brush border and basolateral membranes from rat kidney were incubated with C. collinus
extract and reduction in ATPase activity was assessed. Venous blood samples from human volunteers and rats were incubated with an acetone extract of C. collinus
and plasma potassium was estimated as an assay for sodium-potassium pump activity.
: The mortality was 100% in tests and 17% in controls. Terminal event in test animals was respiratory arrest. Controls had metabolic acidosis, respiratory compensation ,
acidic urine and hyperkalemia. Test animals showed respiratory acidosis, alkaline urine and low blood potassium as compared to controls. C. collinus
extract inhibited ATPase activity in rat kidney. Plasma K +
did not increase in human blood incubated with C. collinus
Conclusions and Implications
: Active principles of C. collinus
inhibit proton pumps in the renal brush border, resulting in type I DRTA in rats. There is no inhibition of sodium-potassium pump activity. Test animals develop respiratory acidosis, and the immediate cause of death is respiratory arrest.