EFFECTS OF PYRIMETHAMINE ON SERUM ALKALINE-PHOSPHATASE AND SOME BONE-MINERAL COMPOSITION OF YOUNG-RATS

The effect of varying doses of pyrimethamine on serum alkaline phospha tase levels, and the composition of some important bone constituents o f young Wistar rats were examined. The drug lowers the levels of serum alkaline phosphatase in rats in a dose dependent manner. Two-week old rats administered a daily dose of 1mg/pyrimethamine/kg body weight ov er a 10-day period had their serum alkaline phosphatase levels reduced by about 38%. Those which received a daily dose of 5mg/kg body weight over the same period had their alkaline phosphatase levels reduced by about 93%. Another group of two week old rats which were given simila r daily doses of pyrimethamine (1mg and 5mg/kg body weight respectivel y) over a period of 20 days showed decreases of 11% and 59% respective ly in their alkaline phosphatase level as compared to the controls. Th e effect of pyrimethamine on alkaline phosphatase appear to diminish w ith the age of the rats. However, the drug did not affect the growth r ate of the rats. The calcium and phosphorus components in the bones we re not significantly altered (p > 0.05). Bone zinc was also not affect ed but the iron and copper levels were significantly reduced (p < 0.05 ) in rats which received pyrimethamine for 20 days. It is suspected th at the reduction in levels of these elements may be due to the effect of the drug on bone marrow as the latter was not removed before the di gestion of the bone for mineral analysis. We suggest that pyrimethamin e, through its effect on alkaline phosphatase activity, has the potent ial to cause bone malformation in foetuses and that older animals may be more resistant to its effect than foetuses.