| Objective: To investigate the mechanism of thyroid follicular cells injury after cardiopulmonary resuscitation(CPR) in rats and the protective effects of Biocoen using the Sprague Dawley rat model of cardial arrest(CA) and CPR induced by asphyxiation combined with iced KCL.Methods: CA was induced by asphyxiation(succinylcholine) and ice-cold 0.5M KC1 in rats and resuscitation began five minutes later. In this experiment, forty-eight male SD rats were randomized into 6 groups: control group (sham), postresuscitation 3h, 6h, 12h, 24h (common treatment group)groups, and Biocoen intervention group ( eash group n=8). Except control group, rats were allowed to reperfuse spontaneously for 3 hours, 6 hours, 12 hours, 24 hours and Biocoen treatment for 24 hours after CPR. Serum concentration of triiodothyronine(T3), tetraiodothyronine(T4), thyroid-stimulating hormone (TSH) were quantitized of each groups respectively. And using the chromametery, the quantity of maleic dialdehyde(MDA) and enzyme activity of superoxide dismutase(SOD)and Na^-K+-ATPase in thyroid tissues were analyzed of the control group and postresuscitation groups. The thyroid cellular apoptosis and injury were assessed by terminal deoxynucleotidyltransferase-mediated dUTP nick endlabeling (TUNEL) and transmission electron microscope(TEM). Fas, Bcl-2, and NF-kB protein expression were studied using immunocytochemistry of e~ach group. Result: Three hours after resuscitation, the serum concentration of T3.T4 began to decline and remain in lower level subsequent 24 hours, while there was only a transient decrease in the serum concentration of TSH at 12th hour. Under TEM, injury of follicular epithelial cells could be observed in post-resuscitation rats. After CPR, quantity of MDA increased greatly (P<0.05), meanwhile, enzyme activity of SOD and Na + -K+-ATPase in thyroid declined significantly compared to the control group (P<0.05). TUNEL-positive thyroid cens could be found at 3 hour post-resuscitation andincreased continuously. There were about 3.10 times TUNEL-positive cells at 24 hour to that of control group . The expression of Fas, Bcl-2 and NF-kB in the thyroid cells were found and were continuous to increase-induced by CA and CPR(P<0.05). They are in positive correlation with the number of TUNEL-positive thyroid cells (r=0.825, 0.879,0.737 respectively, p<0.01).Compared to the common treatment 24 hour group, there was a significant rising of T3 and T4 concentration in serum with a p-value of less than 0.05. The injury of follicular epithelial cells was alleviated. Biocoen intervention group showed a significant reduction of MDA content, and the activity of SOD, Na+-K+-ATPase were increased significantly; The expression of Fas markedly decreased (P<0.05) , so as to the number of TUNEL-positive cells. But the expression of Bcl-2 and NF-kB was not altered.Conclusion: Acute thyroid follicular cells injury happened in rats after CPR. OFR-triggered lipid peroxidation, cellular energy metabolism disturbance and apoptosis may be principal manifestation of thyroid follicular cells injury in post-resuscitation rats. The results of this study demonstrate that Fas, Bcl-2 immunoreactivity and NF-kB expression- induced by CPR seem to be responsible for the thyroid apoptosis. Thyroid follicular cells injury could also be a important factor of nonthyroidal illness syndrome(NTIS), which is associated with prognosis after resuscitation. Biocoen has the function of ameliorating the cellular energy metabolism, clearing the free radicals and decreasing the expression of Fas, thus alleviating the follicular cells injury due to ischemia- reperfusion(I/R). So it plays an important role in the protection of the thyroid tissue after CPR.
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