Heart, Lung and Circulation
32| Volume 20, SUPPLEMENT 2, S14-S15, 2011

Gender Differences in Internal Mammary Artery Vasoconstrictor Responses

      Background: Women have poorer in-hospital outcomes following coronary artery bypass grafting compared with men although the reasons are unclear. Gender-mediated differences in the vascular reactivity of the arterial conduit may contribute to these differential outcomes. This study investigated gender-dependent differences in the vasoconstrictor responses of the internal mammary artery used for coronary artery bypass grafting.
      Methods: Internal mammary artery segments were obtained from patients undergoing coronary artery bypass grafting and subjected to vascular myography. Following assessment of endothelial function, concentration-response curves were determined to noradrenaline, phenylephrine, seotonin, U46619 (thromboxane analogue) and endothelin. The EC50 values for each vasoconstrictor are summarised in the table below, expressed as mean ± SEM (*significant difference between males and females, p < 0.05).
      Tabled 1
      Males (n = 13)Females (n = 7)
      Noradrenaline0.73 ± 0.25 μM0.23 ± 0.40 μM
      Phenylephrine3.36 ± 0.29 μM0.36 ± 0.22 μM*
      U4661911.29 ± 0.12 nM2.32 ± 0.41 nM*
      Serotonin4.08 ± 0.27 μM0.16 μM ± 0.10 μM*
      Endothelin9.36 ± 1.05 nM7.65 ± 1.49 nM
      Conclusion: The internal mammary arteries of women are more sensitive to constriction by thromboxane, phenylephrine and serotonin, compared with men. Ongoing studies are evaluating the molecular mechanisms responsible for these differences.