[Effects of astragalus polysaccharide on cardiac dysfunction in rabbits with severe scald injury]

Objective: To investigate the effects of astragalus polysaccharide (AP) on cardiac dysfunction in rabbits with severe scald injury. Methods: Sixty-four New Zealand white rabbits were divided into pure scald group and AP group according to the random number table, with 32 rabbits in each group. Rabbits in the two groups were all inflicted with 30% total body surface area full-thickness scald on the back. Immediately after injury, rabbits in two groups were intraperitoneally injected with lactated Ringer's solution once for antishock. Rabbits in AP group were intraperitoneally injected with 10 mL AP solution with the dosage of 200 mg/kg 10 min after injury and the following 6 days respectively, once a day. Rabbits in pure scald group were injected with 10 mL normal saline instead. Eight rabbits of each group were respectively selected before injury hour (BIH) 1 and on post injury day(PID) 1, 3, 7, and 14 to collect blood samples from ear marginal vein, and then sacrificed immediately to collect hearts at each time point post injury. The morphology of myocardium was observed after HE staining. The serum content of cardiac troponin I (cTnI) was detected by enzyme-linked immunosorbent assay (ELISA). The serum content of aspartate transaminase (AST), creatine kinase (CK), CK isoenzyme-MB (CK-MB), lactate dehydrogenase (LDH) was detected by fully automatic chemistry analyzer. The content of angiotensin Ⅱ (Ang Ⅱ) in serum and myocardium was detected with radioimmunoassay and the content of endothelin 1 (ET-1) in serum and myocardium was detected by ELISA. Another 8 normal rabbits were sacrificed to detect the content of Ang Ⅱ and ET-1 in the myocardium as the value of the two groups of scalded rabbits at BIH 1. The serum content of superoxide dismutase (SOD) and malondialdehyde (MDA) was detected by ELISA. The values of whole blood viscosity (ηb), reductive viscosity of whole blood (ηr), plasma viscosity (ηp), hematocrit (HCT), erythrocyte rigidity index (TK), erythrocyte aggregation index (EAI), and erythrocyte sedimentation rate (ESR) were detected by fully automatic hematology analyzer. Data were processed with analysis of variance of factorial design, independent sample t test, and Dunnett test. Results: (1) Compared with those in pure scald group, the degrees of cardiomyocyte swelling, steatosis, necrosis and rupture of muscle fiber were significantly alleviated in rabbits of AP group on PID 1 and 3. There was no obvious increase in cell size, no breakage of muscle fiber or infiltration of inflammatory cells in myocardial interstitium on PID 7. The myocardial tissue structure and muscle fiber arrangement returned to normal condition on PID 14, with no interstitial fibroblast hyperplasia or excessive extra cellular matrix deposition. (2) Serum content of cTnI, CK, and LDH of rabbits in AP group was significantly lower than that in pure scald group on PID 1, 3, and 7 (with t values from 2.69 to 13.99, P<0.05 or P<0.01), while there was no significant difference between the two groups on PID 14 (with t values from -0.32 to 0.68, P values above 0.05). Serum content of AST and CK-MB of rabbits in AP group was significantly lower than that in pure scald group on PID 1 and 3 (with t values from 2.21 to 12.65, P<0.05 or P<0.01), while there was no significant difference between the two groups on PID 7 and 14 (with t values from 0.03 to 1.67, P values above 0.05). (3) Serum content of Ang Ⅱ of rabbits in AP group was significantly lower than that in pure scald group from PID 1 to 14 (with t values from 3.38 to 32.58, P values below 0.01). Serum content of ET-1 of rabbits in AP group was significantly lower than that in pure scald group from PID 3 to 14 (with t values from 3.54 to 11.02, P values below 0.01), while there was no obvious difference on PID 1 (t=0.39, P>0.05). Content of Ang Ⅱ and ET-1 in myocardial tissue of rabbits in AP group was significantly lower than that in pure scald group from PID 1 to 7 (with t values from 1.27 to 13.79, P values below 0.01), while there was no obvious difference on PID 14 (with t values respectively 0.07 and 0.81, P values above 0.05). (4) Serum content of SOD of rabbits in AP group was respectively (15.65±2.64), (14.67±0.74), and (8.43±0.56) ng/mL on PID 1, 3, and 7, which was significantly higher than (6.35±0.83), (2.62±0.75), and (2.84±0.41) ng/mL in pure scald group (with t values from -29.79 to -9.10, P values below 0.01); while there was no obvious difference on PID 14 [with (4.02±0.26) ng/mL in pure scald group and (4.11±0.52) ng/mL in AP group, t=-0.01, P>0.05]. Serum content of MDA of rabbits in AP group was respectively (1.31±0.61), (1.72±0.64), and (0.65±0.42) μmol /mL on PID 1, 3, and 7, which was significantly lower than (1.68±0.57), (2.34±0.79), and (1.06±0.32) μmol/mL in pure scald group (with t values from 1.63 to 3.16, P<0.05 or P<0.01), while there was no obvious difference on PID 14 [with (0.31±0.09) μmol/mL in pure scald group and (0.24±0.08) μmol/mL in AP group, t=2.11, P>0.05]. (5) Values of ηb1 and EAI of rabbits in AP group were significantly lower than those in pure scald group from PID 1 to 7 (with t values from 2.718 to 11.170, P<0.05 or P<0.01), while there were no obvious differences on PID 14 (with t values respectively 2.078 and -1.423, P values above 0.05). Values of ηb2 and ηr2 of rabbits in AP group were significantly lower than those in pure scald group on PID 3 and 7 (with t values from 2.178 to 19.205, P<0.05 or P<0.01), while there were no obvious differences on PID 1 and 14 (with t values from -0.730 to 1.320, P values above 0.05 ). Values of ηr1 and ESR of rabbits in AP group were significantly lower than those in pure scald group on PID 3, 7, and 14 (with t values from 3.021 to 8.058, P values below 0.01), while there were no obvious differences on PID 1 (with t values respectively 1.200 and 1.263, P values above 0.05 ). Value of ηp of rabbits in AP group was significantly lower than that in pure scald group on PID 1 (t=2.430, P<0.05), while there were no obvious differences on PID 3, 7, and 14 (with t values from 0.002 to 1.446, P values above 0.05 ). Value of HCT of rabbits in AP group was close to that in pure scald group on PID 1 (t=1.079, P>0.05), and the values were significantly lower than those in pure scald group on PID 3 and 14 (with t values respectively 3.849 and 4.208, P values below 0.01), while the value was significantly higher than that in pure scald group on PID 7 (t=-4.925, P<0.01). Value of TK of rabbits in AP group was lower than that in pure scald group on PID 7 (t=2.847, P<0.05), while there were no obvious differences on PID 1, 3, and 14 (with t values from -1.102 to 0.875, P values above 0.05). Conclusions: AP can alleviate the damage of myocardium of rabbits with severe scald by reducing the production of vasoactive substances Ang Ⅱ and ET-1, decreasing oxidative stress injury by increasing the content of SOD and decreasing the production of MDA, improving blood flow performance and microcirculation perfusion.