摘要：

The corpus luteum (CL) is a temporary endocrine gland formed in the ovary after ovulation. In contrast to the mature follicle, which consists of a cumulus oocyte complex surrounding by a substantial volume of follicular fluid, the corpus luteum is a solid structure of cells. Cell-cell communication and adhesion contribute to CL function, which is mainly to produce progesterone essential for maintaining pregnancy. However, if pregnancy ends or does not take place, the CL undergoes regression (luteolysis), induced by prostaglandinF2alpha (PGF2α). Functional regression of the luteal cells is associated with cessation of their progesterone secretory activity. Subsequently, structural luteolysis takes place with apoptosis of luteal cells and degeneration and processing of the extracellular matrices. Cytochemical studies indicate that acid hydrolases including arylsulfatase(s) are present in lysosomes of regressing luteal cells, and the increase in their activities with the progressive state of luteal regression suggests their roles in luteolysis. While it is tempting to speculate that the arylsulfatase detected in early localization studies (using an artificial substrate, p-nitrocatechol sulfate (NCS)) was arylsulfatase A (ASA) based on its pH optimum of 5, further studies to validate this postulation need to be performed, in particular by methods using an antibody monospecific to ASA. Further, the known substrates of ASA, sulfogalactosylglycerolipid (SGG) and sulfogalactosylceramide (SGC), are implicated in cell adhesion required during CL formation. Therefore, attempts to localize ASA's substrates should also be made. Our immunocytochemistry work revealed the selective presence of ASA in the CL of mouse ovaries, and immunoblotting indicated that CL ASA had a molecular mass of 66 kDa, similar to AS-A of other tissues. CL AS-A was active, capable of desulfating NCS at the optimum pH of 5. To further understand the role of ASA, its levels were determined during CL development in pseudopregnant mice and during luteolysis after cessation of pseudopregnancy (observed by a drop of serum progesterone). Immunocytochemistry, immunoblotting and NCS desulfation activity showed that ASA expression was evident at the onset of pseudopregnancy in the newly formed CL and its level rose steadily during the gland development. The increase in the expression and activity of ASA continued throughout luteolysis. SGG was also present selectively on the luteal cell surface in developed CL, as shown by immunofluorescence of mouse ovary sections as well as high performance thin layer chromatography (HPTLC) of lipids isolated from mouse and pig CL. The identity of the SGG band on the HPTLC plate was further validated by electrospray ionization mass spectrometry. Significantly, SGG disappeared in regressing CL. The SGG immunostaining in regressing CL (as denoted by their morphological properties) on the ovary sections of post-hCG Day-7 superovulated mice was minimal. HPTLC also showed SGG disappearance in lipids isolated from regressing CL of PGF2ï¡-treated estrous pigs. Therefore, lysosomal AS-A may be involved in cell surface remodeling during luteolysis by desulfating SGG, following its endocytosis and targeting to the lysosome. Funded by CIHR, Thailand Research Fund, University of Ottawa International Creative Research grant, WM Keck Foundation, MRF Fund, Development & Promotion of Science/Technology Talented Project Thailand.

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