Inhibition of Angiotensin‐Converting Enzyme Increases Oestradiol Production in Ewes Submitted to Oestrous Synchronization Protocol

This study aimed at evaluating the effects of angiotensin‐converting enzyme inhibitor (enalapril) and angiotensin II antagonist (valsartan) on the oestradiol and progesterone production in ewes submitted to oestrous synchronization protocol. The animals were weighed and randomly divided into three groups (n = 7). A pre‐experiment conducted to verify the effectiveness and toxicity of enalapril (0.5 mg/kg LW) and valsartan (2.2 mg/kg LW) showed that, in the doses used, these drugs were effective in reducing blood pressure without producing toxic effects. In the experiment, all animals were subjected to oestrous synchronization protocol during 12 days. On D10, D11 and D12, animals received saline, enalapril or valsartan (same doses of the pre‐experiment), according to the group randomly divided. The hormonal analysis showed an increase in oestradiol on the last day of the protocol (D12) in animals that received enalapril (p < 0.05), but not in other groups, without changing the concentration of progesterone in any of the treatments. It is concluded that valsartan and enalapril are safe and effective subcutaneously for use in sheep and that the angiotensin‐converting enzyme (ACE) inhibition with enalapril leads to an increase in oestradiol production near ovulation without changing the concentration of progesterone. This shows that ACE inhibition may be a useful tool in reproductive biotechnologies involving induction and synchronization of oestrus and ovulation in sheep.