dinoprost and antarelix

Morphological changes in the corpus luteum following natural and induced luteolysis in the marmoset were investigated by light and electron microscopy. Functional corpora lutea were studied in the mid and late luteal phase, naturally regressed corpora lutea in the early and late follicular phase, and corpora lutea induced to regress by administration of GnRH antagonist or prostaglandin F(2alpha) analogue in the midluteal phase. Natural luteolysis was associated with lutein cell atrophy, condensation of cytoplasmic inclusions and organelles, and accumulation of lipid. GnRH antagonist treatment resulted in aggregations of smooth membranes and myelin-like bodies in the cytoplasm of the lutein cells together with complex aggregations of degenerative cells. After prostaglandin treatment, the lutein cells contained numerous small and large vesicles; as the degenerative changes advanced, these vesicles coalesced into alveolar-type vacuoles, and nuclei involuted. These results show that in the marmoset, natural luteolysis and the two luteolytic treatments reveal different forms of luteal degeneration and cell death, none of which fit the ultrastructural criteria for apoptosis. More emphasis needs to be placed on understanding these predominant nonapoptotic forms of cell death in order to elucidate the process of luteolysis in the primate.

Topics: Animals; Apoptosis; Callithrix; Corpus Luteum; Dinoprost; Female; Gonadotropin-Releasing Hormone; Luteolysis; Microscopy, Electron; Oligopeptides; Prostaglandins

Luteinization is associated with endothelial cell proliferation as part of the extensive angiogenesis necessary to maintain corpus luteum function. However, following luteal demise, the vasculature regresses and the endothelial cells disappear. In the rat corpus luteum, the endothelial cells express high concentrations of insulin-like growth factor-binding protein-3 (IGFBP-3) during luteolysis, suggesting a role of IGFBP-3 during endothelial cell loss. The aim of the present study was to determine the occurrence and location of the messenger ribonucleic acid (mRNA) for IGFBP-3 in the primate corpus luteum, and to determine whether or not induction of luteal regression is associated with changes in localization of the message. Marmoset corpora lutea were studied throughout the cycle. The effects of induced luteolysis were examined 12 h or 24 h after treatment with either a gonadotrophin-releasing hormone antagonist or a prostaglandin F2alpha analogue, administered during the mid-luteal phase. High IGFBP-3 expression was recorded in the endothelial cells of the majority of microvessels and a minority of capillaries surrounding the lutein cells in all functionally active corpora lutea. Expression declined markedly in regressing corpora lutea of the late follicular phase. Expression of the IGFBP-3 mRNA in lutein cells in the control corpus luteum was extremely rare. There were no major differences in the degree and pattern of IGFBP-3 expression as a consequence of induced luteal regression although there was an apparent increase in the number of capillary endothelial cells expressing. Induction of luteolysis resulted in expression in a minority of lutein cells. These results support the concept that IGFBP-3 has an autocrine/paracrine role in regulating various cell types in the primate corpus luteum, including endothelial cells. However, expression of IGFBP-3 mRNA throughout the luteal phase suggests it may regulate angiogenesis and luteal function rather than endothelial cell death and luteolysis.

Topics: Animals; Callithrix; Capillaries; Corpus Luteum; Dinoprost; Endothelium, Vascular; Female; Gene Expression; Gonadotropin-Releasing Hormone; Hormone Antagonists; In Situ Hybridization; Insulin-Like Growth Factor Binding Protein 3; Luteolysis; Oligopeptides; Rats; RNA, Messenger

The polypeptide ubiquitin covalently binds to cytoplasmic proteins and marks them for proteolytic degradation. Ubiquitin is upregulated during apoptosis in some systems. Apoptosis increases during luteolysis but it is not known whether ubiquitin is expressed in regressing corpora lutea. Marmoset ovaries were removed on day 10 of the luteal phase from animals that had received either no treatment, treatment with the PGF2 alpha analogue cloprostenol 24 h earlier, or treatment with the GnRH antagonist antarelix for either 24 or 48 h before ovary collection. Ubiquitin was localized on ovarian sections by immunocytochemistry, and oligonucleosome formation characteristic of apoptosis was examined in isolated corpora lutea by electrophoresis of extracted [32P]DNA. Oligonucleosome formation was low in midluteal corpora lutea on day 10 but increased after induced luteal regression with PGF2 alpha and GnRH antagonist. Nuclear ubiquitin immunoreactivity was found in 1.66 +/- 0.66 steroidogenic cells and cytoplasmic staining was found in 0.4 +/- 0.3 steroidogenic cells (per x 40 field of view) in midluteal phase corpora lutea on day 10. Luteolytic induction with PGF2 alpha significantly increased the number of cells exhibiting cytoplasmic immunoreactivity to 12.24 +/- 1.6 (P < 0.05). Ubiquitin immunoreactivity was not observed after GnRH-induced luteal regression. Apoptotic oligonucleosome formation was found after induced luteal regression with both PGF2 alpha and GnRH antagonist, but ubiquitin upregulation only occurred after PGF2 alpha-induced regression. These results indicate that ubiquitin expression is not specific for luteolysis and is not an indicator of luteal apoptosis, but that the polypeptide does play a role in luteal cellular responses to PGF2 alpha.

Topics: Animals; Apoptosis; Callithrix; Cloprostenol; Corpus Luteum; Dinoprost; Female; Gonadotropin-Releasing Hormone; Immunohistochemistry; Luteolysis; Oligopeptides; Ubiquitins

The mechanism controlling luteal regression in primates is unknown but may involve cell death by apoptosis. Marmoset ovaries containing corpora lutea were studied at different stages of the normal ovarian cycle. Two additional groups of animals underwent induced luteolysis with either the prostaglandin F2 alpha analogue, cloprostenol, or the GnRH antagonist, antarelix, at the mid-luteal phase. Apoptosis in ovarian sections was estimated both by counting the number of cells exhibiting morphological features of apoptosis and by in situ labelling the 3' ends of the DNA fragments with digoxigenin-11-dUTP. Apoptosis was found to be significantly increased in corpora lutea in the early follicular phase (equivalent to the later stage of luteal lifespan) compared with the mid-luteal phase corpora lutea, as judged by either computerized morphometry or 3' end labelling. Apoptosis was also increased by the administration of either cloprostenol or antarelix when using the 3' end labelling end point, but only after cloprostenol when using computerized morphometry. A further form of cell death, characterized by the formation of cytoplasmic vacuoles, was also observed in corpora lutea undergoing both induced and spontaneous regression. These results demonstrate that apoptosis within the primate corpus luteum is increased in both physiological and induced luteal regression. In addition, they show that an alternative form of cell death is involved in both spontaneous and induced luteal regression, although the relative importance of the two mechanisms remains to be determined.

Topics: Animals; Apoptosis; Callithrix; Cell Death; Cloprostenol; Corpus Luteum; Dinoprost; Female; Gonadotropin-Releasing Hormone; Luteolysis; Oligopeptides