Chemical Antagonism of Pteroylglutamic Acid in a Pig; Hematopoietic Effect of Extrinsic and Intrinsic Factors.

Interference with the metabolism of pteroylglutamic acid in the pig, through the use of a crude chemical antagonist, interrupts growth and significantly inhibits the formation of erythrocytes and of granulo-cytes. This interference is removed, despite continued feeding of the antagonist, by administration of a crude source of extrinsic factor (essentially free of PGA), together with normal human gastric juice. This finding affords an experimental animal with which to study the mechanism of action of anti-anemic substances and their functional relation to folic acid; also, a suitable bioassay tool is offered for guiding the isolation of anti-anemic factors of unknown chemical composition.