104 Metabolic, electrolyte and acid-base parameters in blood and fluids of the reproductive tracts during in vivo maturation of bovine oocytes
O. Gungor A B , S. Salman A C , S. Ranjitkar A , D. Zhang A and X. Tian AA University of Connecticut, Storrs, CT, USA
B Bolu Abant Izzet Baysal University, Mudurnu, Bolu, Turkey
C Assiut University, Assiut, Egypt
Reproduction, Fertility and Development 34(2) 289-289 https://doi.org/10.1071/RDv34n2Ab104
Published: 7 December 2021
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of the IETS
Follicular fluid is the microenvironment that supports oocyte maturation and competence. In vivo matured, yet in vitro fertilised and cultured bovine embryos reach blastocyst at 75% compared to their in vitro-matured counterparts at 20–30%. These data suggest a deficiency of in vitro maturation. Here we determined the dynamics of acid-base, ion, and metabolic parameters in blood, fluids of the dominant (largest growing) follicle (FF), oviduct (OF), and uterus (UF) during the window of oocyte maturation. Holstein heifers (n = 24) were oestrus-synchronised with two sets of PGF2α (PG) intramuscular injections 11 days apart on Days −11 and 0. A controlled internal drug release (CIDR) was inserted on Day −6 and removed on Day 1 or 24 h after first dose of the second set of PGF2α. The LH surge was induced by gonadotrophin-releasing hormone (GnRH) given on Day 2. All fluid samples were collected at 24, 48, 60, and 72 h after the second set of PG treatment. The Abbott iSTAT1™ analyser and the CG4+ and CHEM8+ cartridges were used to measure pH, Glucose, lactate, pO2, pCO2 TCO2, HCO3−, base excess, saturated O2, and electrolytes Na+ , K+ , Cl−, iCa2+ , TCO2, urea nitrogen (BUN)/urea, creatinine, haematocrit, and haemoglobin. One-way ANOVA and post hoc pairwise analysis were used to determine differences between groups, and Pearson correlation was used to correlate different parameters between blood and follicular fluid. Significance was set at P < 0.05. Most electrolytes studied, Cl−, K+ and Ca2+ were significantly affected (P < 0.05) by PG injection or CIDR removal in blood and FF. Similarly, Cl− and Na+ also significantly changed in OF and UF across time. However, glucose, lactate, and creatinine changed significantly (P < 0.05) across time points in FF but not in blood. Also significantly changed across time were pO2, pCO2, TCO2, and pH in FF (P < 0.05). Another objective was to determine whether blood parameters could be used to estimate changes in follicular fluid. Most parameters were not significantly correlated across time points except for glucose, Cl−, and creatinine (P < 0.05). Across fluids, Cl− and Na+ were present at comparable levels to maintain charge balance, while K+ and Ca2+ in fluids of the reproductive tracts were approximately twice and half, respectively, of the levels in blood. Urea and creatinine levels were similar in blood and FF but were 2 to 3 times higher in OF and UF. Furthermore, the pO2 in FF was nearly 3 time higher than in jugular venous blood, suggesting low O2 tension during IVM is not appropriate. In conclusion, the iSTAT is a convenient instrument for determining components of bovine blood and FF. Preovulatory follicles undergo significant changes during the window of oocyte maturation and these data can be used as references to improve the in vitro oocyte maturation protocol.
