Abstract
The changes of the endometrial alkaline phosphatase (ALP) along with menstrual cycles were investigated by both enzyme histochemistry and biochemistry. In order to avoid biassed views which may come mostly from insufficient observation on the limited number of cases, the endometrial specimens were obtained from over 180 patients without known abnormalities. Very fine cyclic changes of the ALP, including changes of the intracellular localization pattern, were clearly evidenced by histochemical observations, which were intimately substantiated by biochemical assay. In the proliferative phase, the ALP activity gradually increased to reach its peak at the early secretory phase, right after ovulation. In the mid to late secretory phase, a rather abrupt decrease of the enzyme was evidenced by an inverse increase of the mucin secretion which could be observed by alcian blue staining. On the basis of this clear cyclic change of the endometrial ALP, the mode of hormonal regulation, either by estrogen or by progesterone, on the enzyme activity was discussed.
