Activity of lysosomal hydrolases in human placenta, amnion, decidua and myometrium in the 2nd and 3rd trimester

Six lysosomal hydrolases were studied in tissues of human placenta, amnion, decidua, and myometrium obtained in the 2nd and 3rd trimester. No significant increase in the activity of any lysosomal hydrolase was found in the 3rd-trimester values compared with those obtained in the 2nd trimester. Thus, the increased activity of lysosomal hydrolases in maternal serum at term, previously described in several studies, seems not to be paralleled by a corresponding increase in the activity of these enzymes in the tissues of the pregnant uterus. We speculate that the increase in maternal serum towards term may reflect a macrophage activation initiated by elevated estrogen concentrations in the 3rd trimester.