In an attempt to determine whether lead (Pb) in striated muscle can be taken up by motor axon, mice were injected intramuscularly with a 5% Pb nitrate solution, and the passage of Pb through the tissues was traced with electron microscopy. Thirty minutes after injection in the tibialis anterior muscle, Pb was seen at the sarcolemma and axolemma of the neuromuscular junction (NMJ) and in the adjacent sarcoplasmic reticulum (SR). Pb was also present in the axoplasm and mitochondria of terminal and preterminal motor axons. The presence of Pb was confirmed with x-ray elemental microanalysis. The results indicate that there is a pathway for intramuscular Pb to enter terminal motor axons. This supports the hypothesis that some forms of motor neuron disease (MND) may be due to axonal uptake and retrograde transport of Pb.
After lead (Pb) is injected into striated muscle it binds to the sarcolemma of the neuromuscular junction (NMJ) and crosses into the terminal axons of motor neurons. To find out whether this intra-axonal accumulation of Pb is due to active transport or to diffusion down a concentration gradient, Pb uptake into motor axons of mice was studied at active and inactive NMJs. Twenty-four hours after sciatic nerve crush, 0.1 ml of 5% lead nitrate was injected into the tibialis anterior muscle and 30 min later the location of Pb was sought with electron microscopy and X-ray elemental analysis. A greatly reduced amount of Pb entered the axons after nerve crush compared to non-nerve crush animals, indicating that an active NMJ is required for intra-axonal Pb accumulation. To test if Pb could be entering the axon via recycling vesicles, botulinum toxin (BoTx) was injected into the muscle 24 h before Pb injection. There was no difference in intra-axonal Pb uptake in control and BoTx-injected animals, indicating that Pb is unlikely to use recycled vesicles to enter the axon.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.