Objective: To investigate the difference in the development of acute lung injury after hemorrhagic shock in postpartum and non-pregnant rabbits.
Methods: Hemorrhagic shock/resuscitation was produced on 9 pregnant New-Zealand rabbits postpartum (within 24 hours after giving birth) and 9 non-pregnant controls via carotid artery bleeding and perfusion (i.v.) of lactate Ringer solution for 3 hours. The serum level of cytokine tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10) in the animals were measured at different time points. Lung tissue were taken 3 hours after resuscitation for the determination of malondialdehyde (MDA),the activity of superoxide dismutase (SOD), myeloperoxidase (MPO), dry/wet weight (D/W), nuclear factor-ΚB (NF-ΚB), and mRNA content of intercellular adhesion molecule-1 (ICAM-1).
Results: Serum TNF-α (ng/L) and IL-10 (ng/L) in antepartum pregnant rabbits were not significantly different from non-pregnant rabbits (TNF-α: 87.6 ± 6.8 vs. 83.2 ± 5.3; IL-10: 44.9 ± 3.9 vs. 42.7 ± 3.4, both P > 0.05). However, the serum TNF-α increased significantly after delivery (102.5 ± 8.1 vs. 87.6 ± 6.8, P < 0.05). TNF-α and IL-10 increased 1 hour after shock in both postpartum and non-pregnant rabbits. The serum TNF-α in postpartum rabbits was significant higher than non-pregnant rabbits in each resuscitation period (1 hour: 230.0 ± 14.9 vs. 202.0 ± 10.1, 2.5 hours: 290.0 ± 18.6 vs. 236.0 ± 14.4, 4 hours: 265.0 ± 15.9 vs. 217.0 ± 12.8, all P < 0.05), meanwhile the serum IL-10 in postpartum animals was significantly lower than the non-pregnant controls(1 hour: 104.3 ± 6.9 vs. 135.0 ± 7.8, 2.5 hours: 146.8 ± 9.4 vs. 178.3 ± 11.7, 4 hours: 126.0 ± 7.9 vs. 165.8 ± 9.6, all P < 0.05). The value of MDA, MPO, D/W, NF-ΚB activity and ICAM-1 mRNA content in lung tissue of postpartum rabbits were all significant higher than non-pregnant rabbits after resuscitation [MDA (nmol/mg): 52.6 ± 5.9 vs. 39.4 ± 4.7, MPO (U/mg): 4.62 ± 0.85 vs. 3.26 ± 0.62, D/W: 0.186 ± 0.025 vs. 0.143 ± 0.016, NF-ΚB activity (A value): 0.89 ± 0.27 vs. 0.46 ± 0.15, ICAM-1 mRNA: 4.6 ± 1.2 vs. 2.5 ± 0.7, all P < 0.05], but the activity of SOD (U/mg) was lower (47.8 ± 6.7 vs. 63.5 ± 8.2, P < 0.05) in the controls after resuscitation.
Conclusions: Delivery causes significant increase in serum TNF-α in pregnant rabbits. Inflammatory lung injury is more severe in postpartum rabbits after resuscitation from hemorrhagic shock, and the increased serum level of inflammatory mediators may be part of the mechanism for such difference.