Although it has been widely known that lead can enter through the gastrointestinal tract, we (the writers of this blog) have focused on lead’s effects on the immune system, the brain and development, blood pressure, or on humans and animals as a whole. However, if lead was poisonous to the entire body, then some part of the GI tract would be affected as well through ingestion of lead. Which part of the GI tract would be hit the hardest? Most likely, the organ that has to filter the excess lead out of the blood stream after it is ingested and absorbed: the liver.
The article ‘Lead hepatotoxicity & potential health effects’ by Mudipalli is an overview on the liver problems and diseases that can be caused by exposure to lead. According to the article, primary exposure is through either the respiratory or GI systems, and the absorbed lead is stored mostly in soft tissue and bone. Besides the neurotoxic effects of heavy lead exposure, gastrointestinal colic, which has symptoms of abdominal pain, constipation, and intestinal paralysis, is a consistent early sign of lead exposure. The liver is the first organ to be exposed to absorbed nutrients, because of the portal vein. Lead can cause parts of the liver to become cancerous, or fail in some of its functions, such as drug and cholesterol metabolism. Since the liver is connected to the GI tract, most hepatoxic effects are caused by ingestion, instead of respiration, of lead.
The article goes into detail on the individual mechanisms that damage liver function, such as the reduction in activity of cytochrome p50 (CYP50), which is a major part of drug metabolism. It also discusses some basic studies done to people who are at a higher risk of lead exposure, such as factory workers, gas station attendants, and construction workers. In short, an increased serum lead concentration caused a decrease in CYP50 metabolite excretion. Also, increased levels of lead induce one of the enzymes essential for cholesterol synthesis. The article continues on by detailing the mechanism behind lead’s effect of decreased heme synthesis, hepatic hyperplasia, and increased oxidative stress. It finishes on a positive note, discussing the lead-chelating methods that are therapeutic to lead-induced hepatic toxicity.
This article is very conducive to the rest of the articles posted. While the effects may not seem to be as critical as some of the other organs/systems that were discussed, they still impair liver function, which is dangerous to the entire body. If the liver cannot metabolize drugs on the regular pace, then the threshold of toxic-doses would be lower from everything from drugs like acetaminophen and alcohol to vitamins, like vitamin A and D.
The link to the article can be found here:
http://www.icmr.nic.in/ijmr/2007/december/1205.pdf
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