BIOSYNTHESIS OF GLYCOSAMINOGLYCANS IN THE ENDOMETRIUM DURING THE INITIAL-STAGES OF PREGNANCY OF THE MOUSE

Significant changes in the synthesis of glycosaminoglycans occur durin g the transformation of stromal cells of the endometrium into decidual cells which takes place during the initial stages of pregnancy in mic e. Hyaluronic acid, which is practically absent in the endometrium of virgin mice, increases dramatically on the fifth day of pregnancy, rea ching its maximal concentration on day 6 followed by a 50% decrease on day 7. Changes in hyaluronic acid concentration also occur in pseudop regnant mice indicating that they are not related to the presence of t he embryo in the uterus. The absolute concentration of the sulfated gl ycosaminoglycans, e.g., heparan sulfate, dermatan sulfate and chondroi tin sulfate in the decidua did not change significantly. There was, ho wever, a striking decrease of their biosynthesis in pregnant and pseud opregnant mice when compared to virgin mice, as shown by the use of ra dioactive inorganic sulfate as a precursor for the study of in vivo sy nthesis. A radioautographical analysis confirmed that the highest inco rporation of radioactive sulfate was observed in virgin endometria whe n compared to pregnant ones. These studies also have shown a character istic pattern of labeling in different regions of the endometrium that repeats itself during the different days of pregnancy.