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Right arrow Cardiac - physiology

Ann Thorac Surg 2006;81:1708-1714
© 2006 The Society of Thoracic Surgeons

Original article: Cardiovascular

Effect of Hypoxia-Reoxygenation on Endothelial Function in Porcine Cardiac Microveins

Ying-Ying Dong, MD a , Min Wu, MD a , Anthony P.C. Yim, MD a , Guo-Wei He, MD, PhD a , b , c , *

a Department of Surgery, The Chinese University of Hong Kong, Hong Kong
b Providence Heart Institute, Albert Starr Academic Center, Department of Surgery, Oregon Health and Science University, Portland, Oregon
c Wuhan Heart Institute, The Central Hospital of Wuhan, Wuhan, China

Accepted for publication December 1, 2005.

* Address correspondence to Prof He, Department of Surgery, The Chinese University of Hong Kong, Block B, 5A, Prince of Wales Hospital, Shatin, N.T., Hong Kong SAR, China (Email: gwhe{at}cuhk.edu.hk).

BACKGROUND: The cardiac venous system possesses up to 30% of total coronary vascular resistance and the effect of hypoxia-reoxygenation (H-R) and St Thomas (ST) cardioplegic solution on the vein is unknown. We investigated the effects of H-R, with or without ST, on endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation in porcine cardiac microveins under clinically relevant temperatures.

METHODS: The microveins (diameter 200 to 450 µM) mounted in a myograph were subjected to hypoxia (Po2 < 5 mm Hg) for 30 minutes in Krebs solution (n = 8) or for 60 minutes in Krebs (n = 8) or in ST at 37°C (n = 8) or 4°C (n = 8), followed by 30-minute reoxygenation. The microvein was precontracted with thromboxane A2 mimetic U46619 (–7 log M) and the EDHF-mediated relaxation was induced by bradykinin (–10 to –6 log M) in the presence of indomethacin, NG-nitro-L-arginine, and oxyhemoglobin before and after H-R.

RESULTS: The maximal EDHF-mediated relaxation was significantly reduced after 30-minute hypoxia (38.7 ± 2.0% vs 61.1 ± 2.3%, n = 8, p < 0.001) or 60-minute hypoxia in either Krebs or ST at 37°C (Krebs: 27.8 ± 1.2% vs 56.6 ± 2.5%, n = 8, p < 0.001; ST: 23.8 ± 4.1% vs 57.1 ± 1.5%, n = 8, p < 0.001). The relaxation was significantly less after prolonged H-R in Krebs (p < 0.001). Incubation in Krebs or ST at 4°C also reduced the EDHF-mediated relaxation (Krebs: 25.3 ± 3.3%, n = 8, p < 0.001; ST: 29.1 ± 4.4%, n = 8, p < 0.001) and there were no significant differences between Krebs and ST regarding the relaxation at either 37°C or 4°C (p > 0.05).

CONCLUSIONS: We conclude that (1) H-R impairs EDHF-mediated relaxation in the coronary microveins with more severe injury during prolonged H-R and (2) ST does not provide protection to the EDHF-mediated relaxation impaired by H-R at either 37°C or 4°C.






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