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 nonpregnant 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 acetylcholine, 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.