Pregnancy-associated plasma proteins in pregnant and pseudopregnant rats.

As in the human, the rat pregnancy-associated plasma proteins consisted of four distinct entities as revealed by immunological methods. All showed gradual increases during gestation and rapid disappearance postpartum. They could be physicochemically, although not immunologically, tentatively related to the human pregnancy proteins. None of them was detectable in the serum of rats at various stages of pseudopregnancy, nor in nonpregnant rats.