Abstract 16879: Altered Reactivity and Nitric Oxide Signaling in Isolated Thoracic Ducts From an Ovine Model of Congenital Heart Disease With Increased Pulmonary Blood Flow
Background: Utilizing our ovine model of congenital heart disease (CHD), we have previously demonstrated altered postnatal pulmonary lymphatic development and function in the setting of chronically increased pulmonary blood flow (shunt). These alterations are associated with decreased bioavailable nitric oxide (NOx) in pulmonary lymph effluent. We hypothesized that impaired pulmonary lymph flow is due, in part, to altered lymphatic endothelial NO signaling, and that exogenous NO delivery may augment flow.
Methods: Thoracic duct rings were isolated from 4-week-old lambs (n=7 shunt, 6 normal) to determine tension-diameter properties and vascular reactivity. eNOS protein was measured in primary lymphatic endothelial cells (LECs) by Western. In vivo, pulmonary lymph flow was measured in shunt lambs before and during administration of inhaled NO (iNO, 40 ppm), and NOx was measured in the pulmonary lymph effluent by HPLC.
Results: Ex vivo tension-diameter analysis revealed that in response to norepinephrine, thoracic duct rings from shunt lambs generated a 3.4 times larger increase in vascular tone (p<0.05) compared with rings from normal lambs (n=16 shunt, 15 normal). Compared with normal rings, shunt rings had impaired relaxation in response to acetylcholine (71% vs. 33%, p<0.05). However both normal and shunt rings relaxed similarly in response to SNAP, suggesting that shunt rings have a selective impairment of endothelium-dependent relaxation. eNOS protein was 38% lower in shunt LECs compared to normal (p<0.05). In vivo, change in pulmonary lymph flow (normalized to resistance) was 1.5 times higher in shunt lambs treated with iNO (p<0.05). This was associated with a 3-fold increase in NOx in pulmonary lymph effluent (p<0.05).
Conclusion: Under conditions of chronically increased pulmonary blood flow, perturbed lymphatic function is associated with extrapulmonary (thoracic duct) lymphatic endothelial cell dysfunction with impaired NO signaling. Exogenously delivered iNO enters the pulmonary interstitial fluid and thus the pulmonary lymphatics, and augments relative pulmonary lymph flow in vivo. Mechanisms of lymphatic dysfunction in CHD and the potential use of iNO to improve pulmonary lymphatic function require further investigation.
- © 2013 by American Heart Association, Inc.