Nitric Oxide (NO) and Interleukin-1β (IL-1β) in Follicular Fluid and Their Correlation With Fertilization and Embryo Cleavage


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PROBLEM: Using an IVF model, the goal of the study was to investigate the relationship between follicular fluid (ff) NO and IL-1β levels, as well as their correlation with fertilization of mature oocytes and embryo cleavage rates.
METHOD OF STUDY: Follicular fluid was collected from 17 patients at the time of transvaginal oocyte retrieval following controlled ovarian stimulation. Oocytes harvested from these follicles were followed through fertilization and embryo cleavage. The NO metabolites nitrate/nitrite (NO3/NO2) were measured using the Griess reaction as an indirect assessment of NO activity. IL-1β was measured using a high sensitivity ELISA system (Amersham, UK). The Student's t-test was utilized for unpaired data with the means considered significantly different when P≤0.05.
RESULTS: Follicular fluid NO3/NO2 levels were significantly lower in follicles containing mature oocytes that fertilized (n=30; 9.7±1.0 μM), versus those that did not fertilize (n=23; 15.4±2.4 μM; P<0.05). Follicles that contained oocytes that fertilized and went on to divide beyond the 6 cell stage had significantly lower ff levels of NO3/NO2 (n=18; 7.5±0.9 μM), as compared to ff that contained oocytes that did not fertilize or failed to develop beyond the 5 cell stage (n=35; 14.6±1.7 μM; P<0.01). No correlation was found between ff NO3/NO2 levels (n=28; 13.8±2.0 μM) and ff IL-1β levels (n=28; 0.5±0.08 pg/mL). An analysis of ff IL-1β levels in relation to fertilization and embryo cleavage rates revealed no correlation.
CONCLUSIONS: Lower ff NO3/NO2 levels at the time of oocyte retrieval are associated with adequate fertilization and embryo cleavage rates. In our IVF model, no correlation was found between ff IL-1β levels and ff NO3/NO2, fertilization, or embryo cleavage rates.