Translated title:
Study of the influence of different O2 concentrations in cardiac tissue, in an experimentalmodel of hypoxemia, in newborn piglets.
Summary:
Objective: The evaluation of the effect, on lung and cardiac tissue, of the use
of different oxygen concentration during reoxygenation in an experimental model
of normocapnic hypoxia in newborn piglets.
Materials and Methods: forty male newborn Landrace/Large White piglets
underwent hypoxia and reoxygenation. The piglets were randomly allocated in 4
groups (1-4) according to the received oxygen concentration during
reoxygenation (group 1: 18%, group 2: 21%, group 3: 40%, group 4: 100%).
Furthermore, piglet were allocated in 5 groups (A-E) according with the time
needed to return to stabilization. Blood samples were drawn during
stabilization, hypoxia and reoxygenation, in order to measure levels of
interleukine 6, Ιnterleukine 8 and TNFα. Tissues were immunostained for S100B
and examined for histopathological changes.
Results: In total, the fluctuation of Il-6, Il-8 and TNFα had no significant
differences between groups. However, there was a tendency for difference
(p<0.1) in Il-6 and Il-8. Histological examination of cardiac tissue revealed
alterations (swelling, detachement, endothelial loss, edema, apoptosis,
microthrombosis) in endothelium of vessels in all groups. Analysis of results
between gropus did not reveal significant changes in the following
characteristics: A) interstitial edema, B) wavy arrangement C)
hypereosinophilia D) cytoplasmic vacuolization and E) contraction. Analysis
based on the 5 group allocation (according to resuscitation time) revealed
differences in coagulative necrosis and cytoplasmic vacuolization. Coagulative
necrosis was present in 14,3% in group A, 57,1% in group B and 100% in groups C
and D. Cytoplasmic vacuolization was absent in group A, was present in 57% in
group B and 100% in groups C and D. Significant differences were observed among
groups 1-4 regarding S100B expression. Reactivity for S100B in cardiac cells
was detected in 50%, 50%, 10% and 33% of animals in groups 1 and 2, 3 and 4,
respectively. Marked differences were also observed among groups A-D: 75%, 33%,
12% and 22% of the animals in group 1, 2, 3 and 4, respectively, showed
reactivity for S100B in the heart.
Conclusion: Results of the present study revealed major histological
alterations in myocardium of newborn piglets subjected to hypoxia and
reoxygenation. Levels o Intereleukine-6 and Interleukine-8 differed (p<0.1)
(lower in group 2). Moreover, extreme oxygen concentrations (18%, 100%) were
related to higher levels of apoptosis, whereas room air and moderate oxygen
concentration (40%) seemed to have protective properties against apoptosis.
Furthermore, protective mechanisms of the myocardium during hypoxia are
probably activated. S100B storage in cardiomyocytes correlates with the
different oxygen concentration used during reoxygenation. Moreover protein
S100B, appears to play a role as an early protective factor with a positive
prognostic value in asphyxiated newborn piglets.
Keywords:
Piglets, Oxygen concentration, Perinatal hypoxia, Resuscitation, Hypoxemia5
