The Preliminary Study Of Protective Strategy And Mechanism On Small-for-Size Livers After Major Hepatectomy

Objective: To explore the possibility and method of establishing an ideal and steady rat model for the study of small-for-size livers after major hepatectomy.Method: To calculate the percentage of every hepatic lobe, a total of 20 Sprague-Dawley(SD) rats were undertaken total hepatectomy. Another 20 SD rats were undertaken 90% hepatectomy for methodological and technical training. The rest 20 SD rats were undertaken formal 90% major hepatectomy after Higgins-Anderson's method. Pringle maneuver were applied for every rat during hepatectomy for 30 minutes. The 10-day-survival rate was observed.Results: The right, middle, left lateral and caudate lobe of SD rat liver occupied 23%,36%,32% and 9% of total liver weight respectively. The right inferior and right superior lobe occupied 7% and 16%, the right middle and left middle lobe 24% and 12% with the anterior and posterior caudate lobe 5% and 4% respectively .The operative successive rate was 95%(19/20). 1 case died of anesthetic accident. The 10-day-survival rate was 30%(6/20).Conclusions: Major hepatectomy (90%) with Pringle maneuver is a steady and reliable rat model. It was proved to be an ideal model for the study of small-for-size syndrome. Objective: To explore the protective strategy of Terlipressin on portal hyperperfusion syndrome at the early phase after reperfusion posthepatectomy.Methods: 36 rats were randomly categorized into two groups for the study of hemodynamics of portal hyperperfusion injury: 18 rats in Group Th (Terlipressin group for hemodynamics) and 18 rats in Group Ch (control group for hemodynamics). The hemodynamic parameters were detected before administration of Terlipressin and 30min, 1hour, 2hours after reperfusion. The Group Th were subgrouped into Subgroup Th1/2, Th1 and Th2 in terms of different timepoints, and the Group Ch were also subgrouped into Subgroup Ch1/2, Ch1 and Ch2 respectively. each subgroup contained 6 rats. 20 rats were randomly categorized into two groups for survival study: 10 rats in Group Ts (Terlipressin group for survival) and 10 in Group Cs (control group for survival). All rats were undertaken major hepatectomy(90%) with Pringle maneuver for 30 minutes. Terlipressin was injected into the penile dorsal vein just before appliance of Pringle maneuver in rats of Group Th and Ts. The same amount of sterilized normal saline was injected at the same step in rats of Group Ch and Cs. The survival rate and hemodynamics of rats with small-for-size liver were studied.Results: All rats survived more than 24 hours. The 10-day survival rate of Group Ts(80%) is significantly higher than that of Group Cs, P< 0.05. The portal pressure of Subgroup Th1/2 (13.21±0.32cmH2O) is significantly lower than that of Subgroup Ch1/2 (16±1.03cmH2O) . P< 0.05. The portal pressure reaches its trough level(11.52±0.17cmH2O) in Subgroup Th1, which is significantly lower than that in Subgroup Ch1 (13.5±0.18cmH2O), P<0.05. The portal pressure of Subgroup Ch1/2 is significantly higher compared to its corresponding basic portal pressure P <0.05. The portal blood flow of Subgroup Th1/2 (7.21±0.21 ml/min) and Th1(6.11±0.28ml/min) are significantly lower than their corresponding Subgroup Ch1/2 (9.50±0.35ml/min) and Ch1(6.99±0.19ml/min) ,P< 0.05. Meanwhile, the portal blood flow of Subgroup Ch1/2 is significantly higher compared to its corresponding basic portal blood flow, P < 0.05. The mean blood pressure of Subgroup Th1/2(88.12±1.28mmHg) , Th1(80.83±1.79 mmHg) and Th2 (76.29±0.89 mmHg) are significantly higher than that of their corresponding Subgroup Ch1/2 (57.97±2.01 mmHg) ,Ch1 (59.86±1.75 mmHg) and Ch2(63.71±1.37 mmHg) , P<0.05. Meanwhile, the mean blood pressure of Subgroup Th1/2, Th1 and Th2 are significantly higher than their corresponding basic mean blood pressure, P < 0.05. There are no significant difference of central venous pressure among all of the subgroups in Group Th and their corresponding subgroups in Group Ch. Also there are no significant difference of central venous pressure among all of the subgroups in each group compared to their corresponding basic central venous pressure.Conclusions: The survival rate of rats with small-for-size liver after major hepatectomy can be significantly increased by administration of Terlipressin. We proved that portal hyperperfusion state is transient at the early phase after reperfusion. Terlipressin ameliorates portal hyperperfusion injury by effectively reducing portal pressure and portal blood flow. Objetive: To explore the protective mechanisms of Terlipressin on small-for-size livers at the early phase after major hepatectomy.Methods: The rat model of major hepatectomy(90%) with Pringle maneuver for 30 minutes was used for the study. A total of 60 rats were randomly categorized into 2 groups: 30 rats in Group T(Terlipressin group) and 30 in Group C(control group). Five timepoints of 30min, 2h, 4h, 6h and 24h after reperfusion were designed. A total of 10 subgroups, which were named T1/2, T2, T4, T6,T24 and C1/2, C2, c4, C6, C24 in terms of different timepoints and groups, were divided. Every subgroup contains 6 rats. Samples were collected from every subgroup. Blood samplea were obtained for alanine transaminase (ALT) , aspartate transaminase(AST) and total bilirubin(Tbil) determination. Fresh frozen remnant liver samples were collected for RT-PCR detection of intrahepatic A20 and iNOS at mRNA levels. Paraffin sections of remnant liver were used for HE staining and then observed for morphological changes microscopically. Intracellular expression of Endothelin-l(ET-l), A20 and iNOS were detected by histochemical staining. In situ cell death by TUNEL were also used for detection of apoptosis.Results: AST, ALT and TBil reached their peak levels at 24 hours after reperfusion in each group. The above 3 parameters were significantly reduced in Subgroup T6 and T24 compared to Subgroup C6 and C24, all P<0.05. RT-PCR showed that except the timepoint of 30min after reperfusion A20 expression were upregulated at all of the rest timepoints of Group T with overexpression in Subgroup T2 compared to Group C. The expression of iNOS was all down-regulated in Group T detected by RT-PCR, on the contrary, it was upregulated in group C with overexpression in Subgroup C2 . Microscopic observation showed that the morphological changes of remnant liver in Group T at every timepoint were markedly milder than that in Group C. The apoptosis index in Subgroup C6 was significantly higher than that in Subgroup T6, P<0.05. Histochemical staining showed that A20 expression was strong positive in Subgroup T1/2; A20 expression were stronger at Subgroup T2,T4 and T6 compared to Subgroup C2,C4 and C6;There was no marked difference of A20 expression at 24h after reperfusion in both groups; ET-1 were overexpressed at both Subgroup T1/2 and C1/2, it was markedly down-regulated in Subgroup T24 compared to C24; In Subgroup T1/2 iNOS was overexpressed, but it was markedly down-regulated compared to Subgroup Cl/2, The iNOS expression was down-regulated in Subgroup T24 compared to Subgroup C24.Conclusions: Terlipressin can effectively improve small-for-size liver function at the early phase after reperfusion posthepatectomy. It can also inhibit the early inflammatory response which is related to the down-regulation of iNOS expression. Hepatocyte apoptosis is attenuated by Terlipressin which is related to the up-regulation of A20 expression. Since ET-1 is down-regulated Terlipressin is also supposed to ameliorate sinusoidal mechanical injury hence to help stabilize microcirculatory homeostasis.