MODE OF CELL-DEATH IN THE RAT METRIAL GLAND DURING PERIPARTUM REGRESSION

In the rodent uterus, the metrial gland develops during midpregnancy a nd undergoes regression prior to parturation. The involution of the gl and is reported to be accompanied by the loss of gland cells due to th eir death in situ. Cell death has been classified by using morphologic al criteria into two types: necrosis and apoptosis. To study the mecha nism involved in the peripartum regression of the rat metrial gland, w e examined the mode of cell death in the gland during the last week of gestation. We identified apoptotic cells in the regressing metrial gl and by using DNA fragmentation, in situ DNA 3'-end labeling, and elect ron microscopy. Expression of progesterone receptor (PR) and estrogen receptor (ER) was also demonstrated by immunohistochemistry in the gla nd. The mean weight of metrial gland nodes decreased after day 18 of p regnancy. The apoptotic granulated metrial gland (GMG) cells that were detected by using the in situ DNA 3'-end labeling method were observe d on day 16 of pregnancy, and they increased in number after day 20 of pregnancy. Intense fragmentation of DNA was also found from day 20 to day 22 of pregnancy. Electron microscopy demonstrated apoptotic GMG c ells in the regressing metrial glands, confirming the results of the l abeling studies. Immunohistochemical study revealed that expression of PR and ER, which were localized mainly in fibroblast-like stromal cel ls but not in GMG cells, was almost unchanged during late pregnancy. A poptotic cell death is the major mode of rat metrial gland cell death in the peripartum loss of metrial gland cells. Anat. Rec. 252:369-377, 1998. (C) 1998 Wiley-Liss, Inc.