An improved technique for perfusion of the guinea pig placenta in situ giving viable conditions demonstrated by placental transport of amino acids (L- and D-alanine).

An improved technique for perfusing the fetal guinea pig placenta in situ is described. The result shows linear pressure-flow relations in the rane of 15-50 mm Hg. assumed to be physiological. The preparation shows impermeability for trypan blue. The placental transfer is stereoselective for L-alanine compared with D-alanine. This transfer is ouabain-sensitive, and proceeds against a concentration gradient.