Glycosaminoglycan-promoted muscle reinnervation and insulin-like growth factor-I levels are affected by anti-growth hormone-releasing hormone exposure.

Abstract

The present study shows that exposure to antibodies to growth hormone-releasing hormone (GHRH) partially counteracted the promoting effects of treatment with glycosaminoglycans (GAGs) on muscle reinnervation. Sciatic nerve crush was performed in 2-day-old rats, and reinnervation of the extensor digitorum longus muscle was monitored. The extent of reinnervation was rather poor in saline-treated rats, whereas in GAG-treated rats the extent of muscle reinnervation, the recovery of nerve-evoked muscle twitch tension, and the number of motor neurons reinnervating the extensor digitorum longus muscle were greatly enhanced. In addition, treatment with glycosaminoglycans increased markedly insulin-like growth factor-I (IGF-I) levels in denervated muscles. Both types of stimulatory action exerted by GAGs were affected by concomitant exposure to anti-GHRH, with abolition of IGF-I muscle increase and a smaller enhancement in muscle reinnervation.