ATP CONTENT AND MITOCHONDRIAL DISTRIBUTION DURING IN VITRO MATURATION IN PREPUBERTAL AND ADULT OVINE OOCYTES

"\"Our aim was to investigate energetic status of prepubertal (one-month-old) and adult mammalian . oocytes assessing mitochondrial functionality and ATP content across oocyte maturation. . Oocytes were matured in vitro for 24 h and samples were picked up at 0h (GV), 6h (GV-MI), 21h (MIMII) and 24h (MII). . At each time was assessed 1) nuclear morphology by methanol\\\/PI staining; 2) ATP content by capillary. electrophoresis; 3) functionally active mitochondria using MitoTracker and confocal microscopy (CM). . Prepubertal oocytes showed a delay during maturation compared to the adults (p<0.01). Adult oocytes . reach MI earlier than prepubertal oocytes (65.3% in adult vs 37.9% in prepubertal after 9 h). A similar . trend was observed after 19 h of in vitro culture when MII stage oocytes were 70.4% in adults vs. . 36.4% in prepubertals. MII rates after 24 h were 96.7% and 95.1% in adults and prepubertals . respectively. CM showed a homogeneous fine-to-granular mitochondrial distribution in prepubertal GV . and MII oocytes. Conversely, in adult GV oocytes mitochondrial pattern appeared granular to become . arranged in clusters in MII oocytes. ATP content was lower (p<0.01) in prepubertal (nmol\\\/L, mean±SD, . 9953±278 at 0h, 7844±553 after 7h, 8112±362 after 19h and 11134±274 after 24h) than adult oocytes . (11998±1566 at 0h, 9562±1002 after 7h, 15785±2323 after 19h and 14542±751 after 24h). . In conclusion, both prepubertal and adult oocytes completed maturation after 24 h in culture but . prepubertal oocyte maturation is slow than adults. The distribution and activity of mitochondria in . prepubertal oocytes could explain their reduced competence (Supported by RAS, Biodiversity P5A).\""