Objective: To analyze the changes in body growth, learning and memory capabilities, exercise capacity, and the level of growth hormone (GH) in mice suffering from severe burn.
Methods: One hundred and four healthy BALB/c mice aged from 3 to 4 weeks were divided into normal control group (NC, without treatment) , 7 s burn group (inflicted with 20%TBSA deep partial-thickness burn on the back), 10 s burn group (inflicted with 20%TBSA full-thickness burn on the back), and negative control group (simulating the treatment of two burn groups without injury) according to the random number table, with 26 mice in each group. The body weight, body length, and tail length of 8 mice in each group were measured before burn. Respectively 6 mice of two burn groups were sacrificed on post burn day (PBD) 1, 3, and 7 for determination of serum level of GH with enzyme-linked immunosorbent assay kit. The remaining 8 mice in each of the two burn groups were raised to adulthood. The body weight, body length, and tail length were measured on PBD 62, and the increased percentages of body weight, body length, and tail length were calculated. Morris water maze tests, including escape latency on PBD 66, 67, and 68, frequency of stepping over the platform location and proportion of staying time in the target quadrant on PBD 69, were used to examine the learning and memory capabilities. The time of loaded swimming and the time of pole-climbing on PBD 70 were used to assess the exercise capacity. Above-mentioned indexes were also determined in the two control groups at the same time points. Data were processed with one-way analysis of variance; Welch test was applied when equal variance was not assumed; independent samples t test was applied for paired comparison.
Results: (1) The level of GH of mice in 7 s burn group on PBD 1 [(3 021 ± 506) pg/mL] was lower than that of group NC [(3 728 ± 412) pg/mL, t = 2.656, P < 0.05], while on PBD 3 and 7 [(3 098 ± 503) , (3 199 ± 275) pg/mL] they were close to those of group NC [(3 872 ± 785), (3 301 ± 600) pg/mL, with t values respectively 2.033 and 0.379, P values all above 0.05]. The levels of GH of mice in 10 s burn group on PBD 1, 3, and 7 were respectively (2 859 ± 447), (2 707 ± 151) , and (2 666 ± 222) pg/mL, which were lower than those of group NC (with t values respectively 3.504, 3.571, 2.429, P < 0.05 or P < 0.01). (2) The increased percentage of body weight, body length, and tail length of mice in group NC, 7 s burn group, and 10 s burn group were respectively (155 ± 22) %, (46 ± 6) %, (63 ± 10)%; (112 ± 57) %, (32 ± 12) %, (40 ± 15) %; (106 ± 36) %, (30 ± 8) %, (32 ± 7) %. The increased percentage of body weight of mice in 7 s burn group was close to that in group NC (t = 1.997, P > 0.05), while the increased percentages of other indexes of mice in the two burn groups were lower than those in group NC (with t values from 3.092 to 6.910, P values all below 0.01). (3) The escape latency values of mice in 10 s burn group on PBD 67 and 68 were respectively (33 ± 12), (33 ± 11) s, which were longer than those of group NC [(20 ± 8), (20 ± 7) s, with t values respectively 2.421 and 2.692, P values all below 0.05]. The frequency of stepping over the platform location of mice in 10 s burn group [(1.6 ± 1.8) times] was close to that of group NC [(3.2 ± 1.5) times, t = 1.989, P > 0.05]. The proportion of retention time in the target quadrant of mice in 10 s burn group [ (28 ± 7) %] was shorter than that of group NC[(48 ± 16)%, t = 3.076, P < 0.01]. The escape latency of mice in 7 s burn group on PBD 67 [(30 ± 7) s] was longer than that of group NC (t = 2.659, P < 0.05). The frequency of stepping over the platform location and the proportion of retention time in the target quadrant of mice in 7 s burn group [(2.0 ± 1.1) times, (36 ± 11) %, respectively] were close to those of group NC (with t values respectively 1.930, 1.670, P values all above 0.05). (4) The time of pole-climbing [(30 ± 11) s] and the time of loaded swimming [(38 ± 39) min] of mice in 10 s burn group were shorter than those of group NC [(47 ± 11) s, (122 ± 74) min, with t values respectively 3.108, 2.868, P < 0.05 or P < 0.01]. The time of loaded swimming of mice in 7 s burn group [(47 ± 12) min] was shorter than that of group NC (t = 2.855, P < 0.05), while the time of pole-climbing [(33 ± 14) s] was close to that of group NC (t = 2.044, P > 0.05).
Conclusions: For mice, severe burn can delay body growth, decrease the learning and memory capabilities, decrease exercise capacities, and reduce the serum level of GH.