The Effects Of Methylcobalamin On Denervated Skeletal Muscle Atrophy

Objective: Denervated skeletal muscle atrophy is one ofthe critical complications of the lateral peripheral nerve injuries.Nowadays, how to delay and relieve muscle atrophy is a toughproblem in peripheral nerve territory. Through establishing ratmodels of denervated triceps muscle of calf, we compared theeffects of methylcobalamin administered with intraperitonealinjection, target muscle injection, broken ends of nerveadministration three different schemes on denervated skeletalmuscle.Methods: A total of 60 adult female winster rats, with aweight range 230 to 250g (offered by Hebei MedicalUniversity), was employed in the experiment. The animalswere divided randomly into four groups. Animal models ofdenervated triceps muscle of calf were set up after right tibialnerves were transected. Beginning at the day of the operation,300ug/kg methylcobalamin was injected into rightgastrocnemius muscle in group A every other day; 300μg/kgmethylcobalamin was injected into intraperitoneal in group Bevery other day; 0.02ml isotonic saline solution was injectedinto right gastrocnemius muscle in group C every other day;300μg/kg methylcobalamin was injected into broken ends of nerve by silica gel duct placed extraorgan in group D everyother day. On postoperative 4 and 8 weeks, electromyogram(amplitude of fibrillation potential), wet muscle weight,myocyte diameter and cross sectional area and the number ofapoptotic muscle cells were checked. We analysised the initialdate by SAS 6.12 software package of statistics, P＜0.05 hintsthe significant differences.Results: During the early 2 weeks, skin threptic deficiencywas found in experiment toe of all groups. 4 weekspostoperatively, right sural muscle atrophy appeared. 4 weekspostoperatively, tricipital muscle of calf wet weight was1.68±0.12g in the Group A, 1.41±0.10 g in the Group B,1.18±0.10 g in the Group C and 1.27±0.06 g in the Group D.With significant difference among groups A,B,C and D (P＜0,05). The Group A is better than the other groups. 8 weekspostoperatively, tricipital muscle of calf wet weight was1.42±0.08 g in the Group A, 1.17±0.05 g in the Group B,0.94±0.08 g in the Group C and 1.10±0.07 g in the Group D.Results between group B and group D had no significantdifference (P＞0.05). The difference between each two groups ofthe other groups was statistically significant. Muscle wet weightof the Group A is heaviest, the Group C is lightest. 4 weekspostoperatively, myocyte diameter was 15.47±0.61um in theGroup A＞12.43±0.82um in the Group B, 12.06±0.67um in theGroup D＞10.17±um0.63 in the Group C. Results betweengroup B and group D had no significant difference (P＞0.0.5) The difference between each two groups of the other groups wasstatistically significant. 8 weeks postoperatively, myocytediameter was 13.11±0.62um in the Group A＞11.03±0.91um inthe Group B, 10.83±0.70um in the Group D＞6.740±0.62um inthe Group C. Results between group B and group D had nosignificant difference (P＞0.05). The difference between eachtwo groups of the other groups was statistically significant. 4and 8 weeks postoperatively, results of myocyte cr6ss sectionalarea between group B and group D had no significant difference(P＞0.05). The differences of myocyte cross sectional areabetween each two groups of the other groups were statisticallysignificant. The Group A is better than the other groups. Thephenomena in the MASSON staining: hyperplasia of collagenfiber can be found among muscle slice of all groups. 4 weekspostoperatively, amplitude of fibrillation potential was180.1±6.3μV in the Group A＞142.4±3.8μV in the Group B,142.3±4.1μV in the Group D＞115.1±3.2μV in the Group C.Results between group B and group D had no significantdifference (P＞0.05). The difference between each two groups ofthe other groups was statistically significant. 8 weekspostoperatively, amplitude of fibrillation potential was142.3±4.6μV in the Group A＞113.6±3.4μV in the Group B,113.5±3.7μV in the Group D＞113.5±3.7μV in the Group C.Results between group B and group D had no significantdifference (P＞0.05). The difference between each two groups ofthe other groups was statistically significant. Through TUNEL and the antibody of Bcl-2 protein immunohistochemistrymethod detected apoptosis of triceps muscle of calf experimentside, apoptosis cell of group A is less than group B and groupD, group B and group D is less than group C. Results betweengroup B and group D had no significant difference (P＞0.05)The difference between each two groups of the other groups wasstatistically significant.Conclusion: Methylcobalamin played a role of delayingdenervated muscle from atrophy, creative condition for nerverepear. Comparing methylcobalamin administered with differentschemes we found that methylcobalamin injected through targetmuscle is better than intraperitoneal injection and broken endsof nerve administration.