Utilization of Glutamic Acid in the Presence of High Levels of Pteroylglutamic Acid

Summary The utilization of glutamic acid by Lactobacillus casei and Streptococcus jaecalis R was not affected by increasing the pteroylglutamic acid (PGA) content of the culture medium a thousandfold. The respiration of rat brain slices was not inhibited by adding PGA to the medium at a level of 3×10-4 M, more than 100 times the highest concentration observed in the blood of human subjects following the intravenous injection of 15 mg of PGA. The increased respiration of rat brain slices produced by adding glutamic acid was not reduced by adding PGA to the medium at concentrations of 3×10-3 M and 3×10-4 M. The respiration rate of brain slices of PGA-deficient turkeys, with or without added glutamic acid, was not consistently different from that of brain slices from control birds which had received an adequate dietary supplement of PGA. Brain and kidney tissue slices from rats receiving a high dietary level of PGA respired at the same rate as corresponding tissues from control rats, with or without added glutamic acid.