Localization of Glycogen in the Opacity Characterizing Decidualization in the Cleared Hamster Uterus. ∗

Uteri of pregnant hamsters, and of pseudo-pregnant hamsters in which decidualization has been induced, reveal areas of opacity when viewed by oblique light after clearing by the benzyl-benzoate process. These opacities have been shown to be associated with decidua(1–3), and the presence of glycogen in them has been suggested(2).

During gestation, the first of these areas which appear opaque after clearing develop coincidentally with decidua and mark implantation or decidualization regions prior to visible external swelling. They increase in mass, distending the uterus as localized swellings, late on the sixth day of gestation. They reach a peak in terms of mass per conceptual swelling on the seventh day of development, and begin to regress from the antimesometrial area on the eighth day, i.e., at 7 days and 12 hours.

This paper reports results of chemical analyses of these tissues in comparison to the remainder of the uterus.

Materials and methods. At the relative peak of development of the areas in question (sixth and seventh days), it is possible to make a transverse slit in the uterus at the swollen gestational sites and, with fine forceps, peal from the endometrium the denser mass of the embryo and its surrounding decidua. Examination of material separated by the above technique and then cleared, showed that the peeled out region comprised almost all the opaque material (Fig. 1 and 2). Such “peeled out regions”subsequently are referred to as “opacities,”whether or not they have been subjected to the clearing process and thus actually appear opaque. Samples of the remaining portions of the uterus, from which all mesometrium was removed, were analyzed for comparison.

One series of determinations was carried out on material which had been cleared prior to the separation of the opaque regions.