Lysosomal enzymes in the human endometrium: a biochemical study in untreated and levonorgestrel-treated women

The activities of four lysosomal enzymes, i.e. N-acetyl-beta-hexosaminidase, acid phosphatase, alpha-D-mannosidase and alpha-L-fucosidase have been measured in extracts of endometrial biopsies from untreated and levonorgestrel-treated women of fertile age. Values were compared with protein and DNA content, as well as with lactate dehydrogenase activity, used as reference constituents. In parallel, organ cultures were established from the same endometrial specimens and the release of lysosomal enzymes into the medium was followed. The human endometrium possesses a rich lysosomal equipment, comparable to that found in the human liver. In the untreated cycles, the activities of lysosomal enzymes show a coordinate response to the hormonal changes, decreasing by about 40% from the proliferative to the mid-late secretory phase. Long-term levonorgestrel treatment causes a marked cytoplasmic atrophy, as shown by decreased protein content and lactate dehydrogenase activity, whereas DNA content remains unchanged. In contrast, N-acetyl-beta-hexosaminidase, one of the most active lysosomal enzymes studied, shows a higher specific activity upon levonorgestrel. In both untreated and treated endometria, the organ cultures provide biochemical evidence for a higher release of N-acetyl-beta-hexosaminidase than of lactate dehydrogenase, indicating active secretion of the lysosomal enzyme. During levonorgestrel treatment, there was no correlation between clinically recognized spotting-bleeding patterns and lysosomal enzyme content in, or release from, the endometrium.