| Objective: To investigate the effects of different time interval of ischemia postconditioning on ischemic/reperfusion (I/R) injury and its mechanisms.Methods: 54 white male rabbits were randomly divided into 9 groups that each contained 6 rabbits: sham operation group (group S), ischemia-reperfusion group (group A0,B0),ische- mia postconditioning (I/R) group (group A1, A2, A3, B1, B2, B3). The acute testicular ischemia models were performed by legating unilateral testicular spermatic cord in I/R and IP groups observed under color Dppler ultrasound observation. group A, B were divided on the basis of color Doppler flow signals, The ischemic testes in group I/R regained perfusion immediately, the testes in group IP were subjected to 3 transient episodes of reperfusion /ischemia(R/I)circulations,the time intervals of R/I in group A1 and B2, group A2 and B2, group A3 and B3 were 15s, 30s, 45s. Contrast-enhanced ultrasonographic (CEUS) was performed before operation, reperfusion and 3 days of reperfusion in each group, the parameters includeβ, time-to- peak(TTP), peak-base intensity (PBD), half of declining time (DT/2) were analyzed. After 3 days of reperfusion, testicular malonaldehyde (MDA) and testicular superoxide dismutase (SOD), testosterone in peripheral blood, the activity of Caspase-3, Bcl-2 were observed, The Johnsen's score, apoptosis index (AI), ultrastructure were observed by HE, TUNEL staining and electron microscope respectively.Results: Before reperfusion, the peak level of Contrast-enhanced ultrasonographic Curve in group A0, A1, A2 and A3 showed low and flat and retrusion contrast against group S, in group B0, B1, B2 and B3,they showed more significantly, Intra-group comparison: the parameters showed no significant differences in group A ( A0, A1, A2, A3), B(B0, B1, B2, B3) (P>0.05), after 3 days of reperfusion, the peak level of Contrast-enhanced ultrasonogra-phic Curve in group A0, A1, A2 and A3 elaveted, moved forward contrast against group S, in group B0, B1, B2 and B3, they showed more significantly, Intra-group comparison: the parameters showed no significant differences in groupA ( A0, A1, A2, A3), B (B0, B1, B2, B3) (P>0.05). The content of the testicular MDA increased along with aggravation of the extent of ischemia, Intra-group comparison of the testicular MDA: group A1 and A2 were lower than group A0 significantly (P<0.05), but group A3 and A0 showed no significant differences (P>0.05), group A2 showed lower than group A1 and A3 significantly (P<0.05); group B2 showed significantly lower than group B0 and B3 (P<0.05), but group B1 and B3 showed no significant differences with group B0 (P>0.05). The content of the testicular SOD decreased along with aggravation of the extent of ischemia, Intra-group comparison of the testicular SOD: group A1 and A2 showed higher than group A0 significantly (P<0.05), but group A3 and A0 showed no significant differences (P>0.05), group A2 was higher than group A1 and A3 significantly (P<0.05); group B1 and B2 showed significantly higher than group B0 (P<0.05), but group B3 showed no significant difference with group B0 (P>0.05), group B2 showed significantly higher than group B3 (P<0.05). The content of the testosterone in peripheral blood decreased along with aggravation of the extent of ischemia, Intra-group comparison of the testosterone: group A1 and A2 were higher than group A0 and A3 significantly (P<0.05), but group A3 and A0, group A2 and A2 showed no significant differences (P>0.05), group A2 was higher than group A1 and A3 significantly (P<0.05); group B1 and B2 showed significantly higher than group B0 (P<0.05), but group B3 showed no significant difference with group B0 (P>0.05), group B2 showed significantly higher than group B1 and B3 (P<0.05). The content of the testicular Caspase-3 decreased along with aggravation of the extent of ischemia, Intra-group comparison of the testicular Caspase-3: group A1 and A2 were lower than group A0 significantly (P<0.05), but group A3 and A0 showed no significant differences (P>0.05), group A2 was lower than group A1 and A3 significantly (P<0.05); group B2 showed significantly lower than group B0 (P<0.05), but group B1 and B3 showed no significant difference with group B0 (P>0.05). The content of the testicular Bcl-2 decreased along with aggravation of the extent of ischemia, Intra-group comparison of the testicular Bcl-2: group A2 were higher than group A0, A1, A3 significantly (P<0.05), but there were no significant differences among group A0, A1, A3 (P>0.05), there was no statistically significant in group B (P>0.05). The Johnsen's score decreased along with aggravation of the extent of ischemia, Intra-group comparison of the Johnsen's score: group A2 were higher than group A0, A3 significantly (P<0.05), but there were no significant differences among group A0, A1, A3 (P>0.05), there was no statistically significant in group B (P>0.05). The Apoptosis Index (AI) increased along with aggravation of the extent of ischemia, Intra-group comparison of the AI: group A1 and A2 were lower than group A0 significantly (P<0.05), but group A3 and A0 showed no significant differences (P>0.05), group A2 was lower than group A3 significantly (P<0.05); group B2 was significantly lower than group B0 and B3 (P<0.05), but group B1 and B3 showed no significant difference with group B0 (P>0.05). The Ultrastructure of the Spermatogenic Cell showed significantly different between group A2 showed remarkable alleviated contrast against group A0, A1, A3, there was no statistically significant in group B0, B1, B2, B3.Conclusions:①Ultrasonography especially CEUS can accurately reveal the flow of perfusion in testes, thus can evaluate degree of testicular ischemia objectively.②The degree of testicular ischemia influence the effects of ischemic postconditioning, more gently more better.③D ifferent time intervals of postconditioning have different effects on testicular ischemic/reperfusion injury, 30s/30s effects superior to other time intervals.
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