C. Gordon1, J. Feng1, N. Sellke1, I. Lawandy1, A. Gorvitovskaia1, Y. Liu1, A. Ehsan1, J. G. Fingleton1, F. W. Sellke1 1Rhode Island Hospital,Cardiothoracic/Surgery,Providence, RI, USA
Introduction: We have previously found that cardioplegic arrest and cardiopulmonary bypass (CP/CPB) is associated with impairment of coronary arteriolar response to phenylephrine in non-diabetic (ND) patients. In this study, we further investigated the effects of diabetes on coronary arteriolar response to phenylephrine in the setting of CP/CPB and cardiac surgery.
Methods: Coronary arterioles (90-150 µm in diameter) were harvested pre- and post-CP/CPB from the ND and diabetic (DM) patients (n = 8/group) undergoing cardiac surgery. In-vitro microvascular reactivity was examined in the presence of phenylephrine. The protein expression/localization of the alpha-1 (α -1) adrenergic receptors in the atrial myocardium were measured by Western Blotting and immunohistochemistry.
Results: Phenylephrine (10-9-10 -4 M) induced dose dependent contractile responses in both ND and DM vessels pre and post-CP/CPB. There were no significant differences in the contractile responses to phenylephrine between pre-CP/CPB ND and DM vessels. The post-CP/CPB contractile responses were significantly diminished compared to the pre-CP/CPB in the two groups (P<0.05 vs. pre-CP/CPB). This diminished contractile response was more pronounced in the post-DM vessels than in the post-ND vessels (P<0.05 vs. ND). There were no significant differences in the protein expression of α-1 receptors in the atrial myocardium between the ND and DM tissue or between pre-CP/CPB and post-CP/CPB tissue.
Conclusion: Diabetes is associated with a decreased contractile response of coronary arterioles to phenylephrine in the setting of CP/CPB. This alteration may contribute to the vasomotor dysfunction of coronary microcirculation seen early after CP/CPB in diabetic patients.