Effects of puromycin on incorporation of [ 3H]lysine into protein following hemisection of rat spinal cord

Abstract

Single applications of puromycin into the lesion site of spinal hemisected rats were previously shown to induce transient nerve fiber growth into the lesion. We determined the protein incorporation of [ 3H]lysine into rat spinal cord and brain treated with puromycin in groups of animals 3 h, 12 h, and 1, 3, 7, and 14 days after a left spinal cord hemisection at T2 and compared it to that in saline-treated controls. Each group consisted of two control animals, in which a left spinal hemisection was made at T2 and a Gelfoam sponge soaked in saline implanted in the lesion, and five experimental animals which were implanted with Gelfoam soaked in 1 m m puromycin in saline. One hour prior to utilization, animals were injected subcutaneously with 200 μCi l-[4,5( n)- 3H]lysine monohydrochloride. In brain, no hemispheric or regional differences in protein or soluble fraction radioactivity could be detected in puromycin-treated or control animals. In spinal cord, inhibition of amino acid uptake was not demonstrable 3 h after hemisection, but could be detected at the site of the lesion 6 and 12 h after implantation. Three and 7 days after spinal hemisection, puromycin-treated animals exhibited a larger uptake of amino acid into protein at the lesion site than controls. The results suggest that morphological effects produced by puromycin on spinal cord regeneration may correspond to chemical events occurring within the first 24 h after cord hemisection and puromycin implantation.