Effect of angiotensin-converting enzyme inhibitor on bovine blastocyst rate

The reproductive performance of herds requires in-depth knowledge of the endocrinology of ovarian reproduction in vivo and in vitro. The renin-angiotensin system (RAS) is widely known as regulator of blood pressure, and has been described in several organs and tissues. Captopril is an inhibitor of the angiotensin-converting enzyme (ACE) that prevents angiotensin I (Ang. I) from being converted to angiotensin II (Ang. II). Ang II is capable of reversing the inhibitory effect of follicular cells on the in vitro nuclear maturation of bovine oocytes and improves the cytoplasmic maturation of cumulus-oocyte complexes (COC). The aim of this study was to evaluate the effect of captopril on the bovine blastocyst rate. COCs from female cattle originating from slaughterhouses of the municipality of Teresina-PI, Brazil, were used. A total of 472 COCs were distributed into four experimental groups: G1 (n=58) - 0 µM captopril; G2 (n=83) - 5 µM captopril; G3 (n=81) - 10 µM captopril; and G4 (n=78) 15 µM captopril in the maturation medium. After maturation, 300 COCs were co-incubated with spermatozoa at a temperature of 38.5 oC for 20 h, at 5% CO2. The presumptive zygotes were isolated from the cumulus cells by successive aspirations and washed three times in SOF medium (Nutricell®) supplemented with 5% FBS. Subsequently, they were transferred to a 60 × 15 mm Petri dish containing microdroplets of 100 µL SOF medium (Nutricell®) supplemented with 5% FBS and kept in an oven at 38.5 oC, at 5% CO2, for seven days. Feeding (exchange of 50% of the SOF medium for a previously-stabilized new one) was performed on the fifth day of growth. The blastocyst rate was evaluated after 168 h (D7) of growth, by the nonparametric chi-square test (X2 ). The use of different concentrations of captopril in the growth medium did not change the blastocyst rate, as there was no statistical difference between the experimental groups (G1=37%, G2=48%, G3=53%, and G4=62%). In conclusion, supplementation of the maturation medium with captopril did not improve the blastocyst rate.