UBIQUITIN AND APOPTOSIS IN THE CORPUS-LUTEUM OF THE MARMOSET MONKEY (CALLITHRIX-JACCHUS)

The polypeptide ubiquitin covalently binds to cytoplasmic proteins and marks them for proteolytic degradation. Ubiquitin is upregulated duri ng apoptosis in some systems. Apoptosis increases during luteolysis bu t it is not known whether ubiquitin is expressed in regressing corpora lutea. Marmoset ovaries were removed on day 10 of the luteal phase fr om animals that had received either no treatment, treatment with the P GF(2 alpha) analogue cloprostenol 24h earlier, or treatment with the G nRH 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 [P-32]DNA. Oligonucleosome formation was low in midluteal corpora lutea on day 10 but increased after induced luteal regression with PGF(2 alpha) and G nRH 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 phas e corpora lutea on day 10. Luteolytic induction with PGF(2 alpha) sign ificantly increased the number of cells exhibiting cytoplasmic immunor eactivity to 12.24 +/- 1.6 (P < 0.05). Ubiquitin immunoreactivity was not observed after GnRH-induced luteal regression. Apoptotic oligonucl eosome formation was found after induced luteal regression with both P GF(2 alpha) and GnRH antagonist, but ubiquitin upregulation only occur red after PGF(2 alpha x)-induced regression. These results indicate th at ubiquitin expression is not specific for luteolysis and is not an i ndicator of luteal apoptosis, but that the polypeptide does play a rol e in luteal cellular responses to PGF(2 alpha).