Studies on 17beta-hydroxysteroid dehydrogenase in human endometrium and endometrial carcinoma I. Subcellular distribution and variations of specific enzyme activity.

: Specific activity of 17beta-hydroxysteroid dehydrogenase (17beta-HSD) was measured in subcellular fractions of normal endometrium at different phases of the menstrual cycle, and of endometrial carcinoma at different degrees of differentiation. The purity of fractions was determined by marker enzymes, RNA/DNA ratio or electronmicrographs. Both in normal and neoplastic tissue 17beta-HSD activity was located mainly in mitochrondria and microsomal enzyme is bound tightly to the membranes of the endoplasmic reticulum. While in normal endometrium specific enzyme activity in subcellular fractions depended on the phase of the cycle, in endometrial carcinoma it depended on the degree of differtiation of the tumours. The highest values of 17beta-HSD activity were found in mitochondria and microsomes of early secretory endometrium (factor in mitochondria and microsomes of early secretory endometrium (factor 10 as compared to proliferative endometrium) and in particulate fractions of well differentiated carcinoma (factor 10 to greater than 10 as compared to undifferentiated carcinoma).