Selective Localization of Evans Blue (T1824) in Subplacental Portions of Entoderm in the Rat. ∗

Discussion and Summary

The above described selective localization of Evans blue is of special interest since this localization in epithelial cells is in contrast to that observed when the dye concentrates selectively in and about carcinomas or sarcomas which localization is in mesoblastic cells of the stroma—i. e., fibroblasts and macrophages. Such selective concentration might denote a special physiologic property of a portion of the visceral entoderm in the type of placentation represented in the rat.

Goldmann 3 in his studies on intravital staining showed that trypan blue was concentrated in all of the entoderm in mice. However, storage of this dye was also observed by him in all of the reticulo-endothelial system, of the mother, because of the relative enormous doses of the dye administered. Such very large doses precluded the demonstration of selective affinity for the dye on the part of certain tissues, as for example, the subplacental visceral entoderm. In his excellent monograph entitled “The Localization of Disease” Burrows 4 illustrates in colors the exposed viscera of a pregnant rat injected with isamine blue. The uterine horns have not been opened and the dye appears localized in and about the placenta. The illustration was published to indicate specific concentration of the dye in the placenta. From our own studies in which the gross appearance of the unopened pregnant uterus was similar to that depicted by Burrows, we would raise the question of whether the dye he used was also concentrated not in the placenta primarily, but rather in the subjacent visceral entoderm as occurred with Evans blue in the observations reported above.