Submission Number: UDI-4-18-4

Abstract Number: 542

COMPARISON BETWEEN DIFFERENT PROTOCOLS USING STRONTIUM FOR ACTIVATING BOVINE OOCYTES.

Claudia LV Leal, Simone C Meo and Joaquim M Garcia

Depto. de Medicina Veterinária Preventiva e Reprodução Animal, FCAV–UNESP, Jaboticabal–SP, Brazil ¹

Abstract:
Many different treatments have been tested to improve activation rates of oocytes. Strontium has been shown to be quite effective in mice, however, no data are available in cattle. The aim of the present work was to evaluate different protocols using strontium for bovine oocyte activation comparing their abilities to produce activation and cleavage. Oocytes were matured in vitro in TCM 199 medium supplemented with pyruvate, FSH, LH, estradiol, antibiotics and 10% FCS. After 27-28 hours of maturation, oocytes were stripped of cumulus cells, selected for the presence of the first polar body and then randomly assigned to the treatments: 10 mM SrCl₂ (in Ca²⁺-free TALP medium) for 4, 12 or 30 h (S4, S12, S30, respectively); electric pulse (P) 3 pulses of 1.0 kV/cm for 100 s, 5 min apart (pulse medium: 0.28 M inositol, 100 M CaCl₂, 100 M MgSO₄, 10 mM histidine, pH 7.0); and the combinations PS4, S4P and PS30. After each treatment, oocytes were placed in culture in TCM 199 + 5mg/ml fatty acid-free BSA. Oocytes remained in culture for 24 h or 48 h to assess activation and cleavage rates, respectively, when they were stained with 10 g/ml Hoechst 33342 to observe presence of nuclei. All cultures were at 38.5C in 5% CO2 in air. Regarding activation, all single treatments (S4, S12, S30 and P) presented similar rates (83-89%, p>0.05). The combined treatments PS4 and PS30 activated significantly less oocytes (60-68%, p<0.05) than any single treatment, while S4P was similar to all of them (88%, p>0.05). Considering cleavage, P (53%) was better (p<0.05) than all single S treatments (6-24%). The combined treatments SP4 and PS30 (65% and 44%, respectively) did not differ from P (p>0.05), however, they improved cleavage rates when compared to S alone (p<0.05). SP4 was the best of the combined treatments (p<0.05). It can be concluded that strontium is able to induce activation of aged bovine oocytes with rates similar to traditional electroactivation. Combination of strontium with electroactivation does not improve activation or cleavage rates, however, when combining short exposure to strontium (4 h) and electric pulse, slightly superior cleavage rates are observed. More studies are needed to understand the role of strontium in activating bovine oocytes. This work was supported by FAPESP, Brazil, grant n. 98/12085-1. .

Keywords: strontium, activation, oocyte, bovine

This abstract is being presented at: 8:00 AM in session:
IVF /ART II