Organ preservation
Nitroglycerin Reperfusion Reduces Ischemia-Reperfusion Injury in Non-Heart-Beating Donor Lungs

https://doi.org/10.1016/j.healun.2005.02.013Get rights and content

Background

Lung transplantation is severely limited by an inadequate supply of lungs from brain-dead donors. A potential solution is use of lungs from non-heart-beating donors (NHBDs) with retrieval at intervals after circulatory arrest and death. A warm ischemic period with concomitant reperfusion injury is a major limiting factor in the transplantation of lungs retrieved from NHBDs. We hypothesized that the administration of the nitric oxide-donor nitroglycerin to lungs from NHBDs would reduce ischemia-reperfusion injury by activation of guanylate cyclase to form guanosine 3′,5′-cyclic monophosphate (cGMP).

Methods

An in situ isolated perfused rat lung model was used. Lungs were retrieved from rats at varying intervals after circulatory arrest and death. Lungs were either ventilated with O2 in situ or not ventilated. Lungs were reperfused at intervals after death with Earle’s solution with or without nitroglycerin (0.1 mg/ml). Lung ischemia-reperfusion injury was assessed by capillary filtration coefficient, wet-to-dry lung weight ratio, and pulmonary hemodynamics. Tissue levels of adenine nucleotides and cGMP concentrations were measured by high-performance liquid chromatography and enzyme immunoassay, respectively.

Results

Reperfusion with nitroglycerin decreased capillary filtration coefficient compared with reperfusion without nitroglycerin at all post-mortem ischemic times, irrespective of pre-harvest ventilation. cGMP levels increased significantly with nitroglycerin-reperfusion and attenuated decreases in high-energy adenine nucleotides.

Conclusions

Reperfusion of lungs with nitroglycerin may facilitate safe lung transplantation from NHBDs by reducing capillary leak after reperfusion.

Section snippets

Isolated Perfused Lung Model

The IPRLM first described by Gaar et al29 and modified by Drake et al30 provides a sensitive and reproducible method to assess alterations in the permeability of the pulmonary microcirculation, the critical initial phase of lung IRI. After determining Kfc in rat lungs,31 investigators have used this preparation to further characterize lung reperfusion injury.32, 33, 34, 35 The specific details of our preparation have been outlined previously.4

Briefly, male Sprague-Dawley rats weighing 250 to

Kfc

Changes in microvascular permeability as measured by Kfc are shown in Figure 1. Kfc increased in lungs as the post-mortem ischemic time increased. The elevation in Kfc was slightly attenuated in lungs retrieved 120 minutes post-mortem with O2 ventilation alone. Reperfusion with NTG resulted in substantially decreased Kfc of lungs retrieved 120 minutes post-mortem, regardless of cadaver ventilation. Kfc could not be determined in lungs retrieved >2 hours post-mortem unless they were reperfused

Discussion

Endothelium-derived NO is a product of L-arginine conversion to citrulline. NO acts as a signaling molecule to maintain endothelial capillary permeability, reduce platelet aggregation, and inhibit neutrophil adhesion to the endothelial surface.25, 38 Endogenous and exogenous NO stimulate soluble guanylate cyclase to produce cGMP.23, 39 Increased levels of cGMP induce smooth muscle relaxation and vasodilation23, 40 via changes in smooth muscle cytosolic calcium.41, 42

Pinsky et al and other

Conclusion

Increased capillary permeability of lungs retrieved from NHBD rat lungs can be almost completely ameliorated after up to 120 minutes of post-mortem ischemic time if the lungs are reperfused with a NTG-supplemented solution. Marginal yet significant attenuation of IRI was also observed in NTG-reperfused lungs beyond 2 hours of pre-harvest ventilation with O2. The mechanism through which this occurs appears to involve an increase in intracellular cGMP concentration. Stimulation of cGMP pathways

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    This study was supported by NIH R01 HL63159-01A2.

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