Effect of the in vitro maturation medium on equine oocytes: comparison of follicular fluid and oestrous mare serum

Hematochemical Patterns in Follicular Fluid and Blood Stream in Cycling Mares: A Comparative Note

The aim of this study was to verify the existence of possible cross-talk between biochemical contents of follicular fluid (FF) and systemic concentrations according to the follicular development of the metabolites: glucose (GLU), lactate (LACT), cholesterol (CHOL), triglycerides (TG), total bilirubin (T BIL), blood urea nitrogen (BUN), and creatinine (CREAT); enzymatic activities: gamma-glutamyl transferase (GGT), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and aspartate aminotransferase (AST); electrolytes: calcium (Ca), phosphorus (P), sodium (Na), chloride (Cl), potassium (K), magnesium (Mg), and iron (Fe); total proteins (TP) and their fractions: albumin (ALB), α1-, α2-, β-, and γ-globulins (GLOB) of FF and blood strain and their correlations with follicular size in cycling mares. Systemic concentrations of GLU, T BIL, BUN, Fe, TP, ALB, α-1, and α-2 and δ-GLOB and of ALP, GGT, and AST activities were higher than in the FF (P < .05); LACT, CHOL, and TG were higher in FF than systemic ones (P < .05). Glucose, CHOL, TG, LACT, and T BIL were higher in large follicles than in medium and small follicles (P < .05); however, BUN, Fe, ALP, and AST were lower in large follicles than in medium or small follicles (P < .05). Alkaline phosphatase, GGT, and AST activities decreased in medium and large follicles compared with small follicles (P < .05). These results suggest that the metabolic, enzymatic, electrolytic, and protein composition of FF of growing follicles could occur according to the bloodstream changes; hence, it is possible to presume that the nutritional environment of oocyte and follicular cells could improve the clinical diagnoses of infertility in the mare.

In vitro equine oocyte maturation in pure follicular fluid plus interleukin-1 and fertilization following ICSI

The interleukin-1 (IL-1) system is thought to be involved in periovulatory events in the mare. Previous in vivo studies have demonstrated that IL-1beta induces oocyte maturation, but depresses the pregnancy rate 14 days after ovulation. To better understand the role of IL-1 in oocyte maturation and fertilization, the effects of IL-1 on the in vitro maturation rate of equine oocytes in pure follicular fluid were evaluated and fertilization rate assessed following intracytoplasmic sperm injection (ICSI). Oocytes collected from slaughterhouse ovaries were cultured in four different media for 30 h prior to fertilization. Two experiments were performed, each using three maturation media as the experimental treatments. Medium 1 was pure follicular fluid from subordinate follicles. Medium 2 was medium 1 plus 50 ng/ml recombinant human IL-1beta. Medium 3 was pure follicular fluid collected from mares administered crude equine gonadotropin (CEG). Medium 4 was medium 2 plus 50 ng/ml of recombinant human IL-1 receptor antagonist. Media 1, 2 and 3 were compared in experiment 1. In experiment 2, media 1, 2 and 4 were compared. After maturation, metaphase II oocytes were submitted to microinjection and assessed for signs of fertilization. In experiment 1, 101 oocytes were evaluated. The rate of polar body extrusion was 66, 51 and 68% and the proportions of normally fertilized oocytes after ICSI were 40, 18 and 38% for media 1, 2 and 3, respectively. In experiment 2, 122 oocytes were evaluated. The rate of polar body extrusion was 55, 48 and 42% and the proportions showing normal fertilization after ICSI were 14, 25 and 29% for media 1, 2 and 4, respectively. There was no positive effect of IL-1beta on maturation in both experiments, but the fertilization rate and percentage of embryos reaching four-cell were low in the presence of IL-1beta, indicating that this cytokine may interfere with fertilization and early embryo development.