[Pharmacological studies on degeneration and regeneration of the peripheral nerves. (2) Effects of methylcobalamin on mitosis of Schwann cells and incorporation of labeled amino acid into protein fractions of crushed sciatic nerve in rats].

Male Wistar rats (140 to 150 g) in which the unilateral sciatic nerve had been crushed were treated consecutively with methylcobalamin (5, 50 and 500 mug/kg/day i.p.) or saline immediately after the nerve-crush. Thereafter, they were periodically sacrificed for biochemical and histological examinations. At different intervals after the nerve-crush, L-leucine-4,5-T (20 mu Ci/100g, specific activity 15 mCi/m mole) or L-leucine -14C(U) (15 muCi/100g, specific activity 270 mCi/m mole) was given i.p. to some rats of each group and 3 hr later they were sacrificed to determine the rate of leucine incorporation into protein fractions of the crushed nerve and the denervated muscles. The nerve and muscles of the contralateral side served as control. Longitudinal sections of proximal and distal stumps of the sciatic nerve were prepared and stained with hematoxylin and eosin. As compared with saline group, repeated injections of 5, 50 and 500 mug/kg/day of methyl-cobalamin caused a significant increase of the in vivo incorporation of radioactive leucine into the protein fraction of the crushed sciatic nerve 5 to 7 days after the crush. In contrast, a recovery of the increased incorporation of leucine into the crushed nerve was more rapid in methylcobalamin groups than in the saline group. On the other hand, methylcobalamin (5 approximately 500 mug/kg/day i.p.) had no significant effect on the leucine incorporation into the denervated muscles (m. gastrocnemius, m. tibialis anterior and m. soleus). In addition, consecutive injections of methylcobalamin (5 approximately 500 mug/kg/day) did not affect the mitosis of Schwann cells during the period of Wallerian degeneration of the crushed sciatic nerve. These results suggest that methylcobalamin possesses a stimulating effect on proteosynthesis in Schwann cells at the initial stage of axon regeneration and it may facilitate neural regeneration.