Rat folic acid reductase activity during the perinatal period,in newborns,and after trimethoprim administration

Summary The folic acid reductase activity in various organs of adult rats was studied in comparison to pregnant females (20th day of gestation) and fetal rats. The enzyme activities in the tissues of pregnant rats were in general about 30% higher than in normal adults. Fetal rats also possess the ability to catalyze the reduction of dihydrofolic acid, but it is evident that the liver and kidney have a considerably reduced capacity to form tetrahydrofolate. The folic acid reductase activity in liver and kidney rises for 10 days after birth and then declines to normal enzyme levels by the 4th week of life.Further studies concerning the interaction between trimethoprim and folic acid reductase in adult rats demonstrate that an oral dose of 5 or 50 mg/kg results in about a 30% increase of folic acid reductase activity in liver and kidney. The experiments suggest that there is a stimulation of enzyme synthesis following trimethoprim administration; because, the trimethoprim induced increase of the reductase activity is blocked by the administration of either puromycin or actinomycin D.