Objective: The evaluation of the expression of S100B protein, in the swine heart in an experimental model of hypoxia - reoxygenation.
Methods: Normocapnic hypoxia was induced in 40 male Landrace/Large White neonatal piglets by decreasing the inspired concentration of oxygen to 6-8%. When animals developed bradycardia or severe hypotension, reoxygenation was initiated. Piglets were allocated in four groups of 10, according to the oxygen concentration they were reoxygenated with: Group 1, 2, 3 and 4 resuscitated with 18%, 21%, 40% and 100% oxygen, respectively. The animals were further classified into 4 groups according with the time required for reoxygenation: group A (<15 min); group B (16-60 min); group C (>60 min); group D (deceased animals).
Results: Immunostaining for S100B protein was detected in 14 out of the 40 heart samples (35%), both inside the cytoplasm of cardiomyocytes and as globular deposits in the interstitial spaces. 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.
Conclusions: Expression of S100B protein occurred in the heart of some of newborn piglets following severe hypoxia. S100B storage in cardiomyocytes correlates with the different oxygen concentration used during reoxygenation, being higher in piglets reoxygenated with 18% and 21%, and lower in animals reoxygenated with 40% oxygen. Intermediate levels of S100B expression were found in 100% O2-treated animals. The finding of a higher percentage of S100B-immunoreactive hearts in piglets with a fast recovery and the detection of a decreased reactivity in animals with a slow and a very slow recovery clearly indicates S100B protein as an early protective factor with a positive prognostic value in asphyxiated newborn piglets.