Biosynthesis of glycosaminoglycans in the endometrium during the initial stages of pregnancy of the mouse.

Significant changes in the synthesis of glycosaminoglycans occur during the transformation of stromal cells of the endometrium into decidual cells which takes place during the initial stages of pregnancy in mice. Hyaluronic acid, which is practically absent in the endometrium of virgin mice, increases dramatically on the fifth day of pregnancy, reaching its maximal concentration on day 6 followed by a 50% decrease on day 7. Changes in hyaluronic acid concentration also occur in pseudopregnant mice indicating that they are not related to the presence of the embryo in the uterus. The absolute concentration of the sulfated glycosaminoglycans, e.g., heparan sulfate, dermatan sulfate and chondroitin sulfate in the decidua did not change significantly. There was, however, a striking decrease of their biosynthesis in pregnant and pseudopregnant mice when compared to virgin mice, as shown by the use of radioactive inorganic sulfate as a precursor for the study of in vivo synthesis. A radioautographical analysis confirmed that the highest incorporation of radioactive sulfate was observed in virgin endometria when compared to pregnant ones. These studies also have shown a characteristic pattern of labeling in different regions of the endometrium that repeats itself during the different days of pregnancy.