Changes in vascular reactivity following subrenal aortic constriction in pregnant and nonpregnant rats

Objective: The present study was designed to determine whether or not subrenal aortic coarctation (SAC) is able to modify aorta reactivity in pregnant rats. Methods: Wistar female rats were subjected to SAC, and the responses to phenylephrine and acetylcholine of aortic segments above (thoracic) and below (abdominal) the coarctation from pregnant and non-pregnant rats were explored. Results: Contractile responses to phenylephrine and relaxant responses to acetylcholine were similar in the thoracic segment from pregnant and non-pregnant SAC rats, whereas both kinds of response were higher in the abdominal segment from pregnant rats (p < 0.05). L-NAME (a nitric oxide synthase inhibitor) increased the effect of phenylephrine only in the aortic rings from pregnant animals (p < 0.05) and in general abolished the response to acetyl-choline, with the exception of the abdominal segment from pregnant rats, in which only a partial inhibition was observed (p < 0.05). Indomethacin inhibited the contractile response to phenylephrine and increased the relaxant activity to acetylcholine in both aortic segments from the two groups of animals (p < 0.05). Conclusion: The lower contractile response to adrenergic agonists and higher relaxant response to acetylcholine that are associated with normal pregnancy are lost as a consequence of the coarctation procedure. Changes in the production of endothelial nitric oxide and contractile prostanoids appear to be associated with the vascular disturbances observed in SAC rats.