Morphological studies of the stromal changes after artificial induction of the decidual reaction in rats.

Stromal changes during early oil-induced decidualization were studied. Rats previously sensitized with estradiol after an experimental delay were used. Among the initial stromal characteristics that developed after induction, the following sequence was found: ultrastructural alterations of stromal cell nucleoli, extracellular edema, and Pontamine Blue Reaction (PBR). The results suggest that stromal cell differentiation into decidual cells is initiated before the PBR becomes visible. This is in accordance with biochemical and morphological findings at blastocyst implantation. The appearance of an edema before the PBR furthermore suggests that also the increase in vascular permeability is initiated early and takes place slowly. The functional relationships between the vascular and stromal cell changes are, however, not determinable with the method used.