Toxicity and Detoxification

What are Toxicity and Detoxification?

Although the subject of toxicity deserves a complex discussion of biochemical pathways, we're not going to indulge in a description of what many would find painful detail. Instead, the subject of toxicity will cover where toxins come from, how they affect pets and what can be done about them. The section on Poisoning has more detail you may find useful.

Unrecognized toxins
Unrecognized toxins are often found in pet foods and treats, including dyes and chemical preservatives (BHT, BHA, and ethoxyquin) that are legally allowed in the food. Pet foods also contain meats and fish with unrecognized chemical residues from growth stimulants, antibiotics, dewormers, and pesticides. Fish, especially when it is farm-raised, contains PCBs and heavy metals such as mercury.

Foods and treats labeled “natural” are not necessarily free of toxins. Many “natural” products contain meats, grains, or fish with residues of growth accelerants, antibiotics, herbicides, and pesticides. Natural is not synonymous with “healthy” or “organic.”

Well-known toxins
In addition to the hidden toxins pets are exposed to, they also consume or are injected with many products known to be toxic. Some well-known toxins are listed below as chemical toxins or as medications and veterinary products:

Potentially toxic chemicals

• 2,4-D
• antifreeze
• ammonia
• carbamate
• chlorinated hydrocarbons
• ethylene glycol
• hydrogen sulfide
• lead
• fluoride
• fungicides
• insecticides
• mercury
• metaldehyde
• organophosphates
• organochlorines insecticides
• phosphorus
• reserpine
• rodenticides
• strychnine
• wood preservatives
• zinc phosphide

Potentially toxic medications and veterinary products
Some vaccines, medications, and anesthetics with great healing potential also have the potential to be toxic. These products require veterinary guidance to be maximally safe and beneficial. Your veterinarian will work to reduce potential problems by regulating the amount and frequency with which they are administered. Your pet may be asked to come in for blood tests and exams to ensure all is going well.

Examples of some common therapeutic products with the potential to be toxic are:

• vaccines with adjuvants
• barbiturates: Valium
• nonsteroidal antiinflammatory drugs (NSAIDs): Rimadyl, EtoGesic, Tylenol
• antibiotics: tetracycline, sulfonamides
• anti-seizure medications: phenobarbital, primidone
• anti-parasitic medications: amitraz, pyrethrin
• anesthetics: halothane, isoflurane

The liver gets rid of toxins
In all living systems, foods enter and wastes exit. Sounds simple, but consuming food and discharging waste is an interaction of stomach, intestines, gall bladder, pancreas, kidneys, skin, lungs, and nervous system. These organs are essential for digestion and elimination, but it is the liver that does the most to rid pets of toxins.

To prevent damage from toxins, the liver passes all materials that aren’t nutrients through two phases that change them chemically. In Phase 1, liver enzymes (Cytochrome P 450’s enzymes) oxidize, reduce, or hydrolyze materials. Phase 1 produces some materials that are harmless and some materials that are still toxic and able to harm the liver itself. For protection, the liver has an internal system of antioxidants, such as glutathione. In addition, the liver processes materials as fast as it can from Phase 1 into Phase 2. In Phase 2, molecules are conjugated, which means something is added so that the intestines or kidneys can excrete them.

The liver’s commanding position
The liver sits in the abdomen just above the stomach and receives all the blood after it that sweeps through the stomach and intestines. In fact, the liver receives blood before blood is carried to the brain, heart, or anywhere else. With this routing, the liver can process all nonfood materials through Phases 1 & 2, protecting the body from damage.

Why the liver cannot detoxify everything
Unfortunately, some materials that enter the body are not detoxified. This occurs because

• there is too much of the material for the liver to process (alcohol overdose, phenobarb overdose),
• the liver cells are genetically abnormal and cannot function (copper storage hepatopathy, microhepatia)
• the liver cells are damaged and cannot function (hepatitis, hepatic cirrhosis),
• the material doesn’t reach the liver (portosystemic shunt), or
• the liver didn’t evolve with enzymes to address the toxin.

When the liver cannot detoxify materials, the kidneys and intestines cannot recognize the materials and excrete them. These toxic materials remain within the body where they can cause illness.

Where toxic materials are stored
Some toxic materials gravitate to particular organs; others are dispersed generally throughout the body. For example, Bedlington terriers and Westies often have toxins that collect in their livers. These breeds have a genetic disease that prevents some of them from processing copper. Toxic levels of copper collect within the liver, which swells, becoming large and painful. Copper toxicosis is eventually fatal.

Other forms of toxic material deposition are much more subtle because toxic materials are scattered throughout the brain, heart, kidneys, spleen, etc. When toxins are scattered, pets tend to exhibit more generalized forms of illness and it is difficult to identify precisely what is causing their poor health. If toxin exposures continue, eventually cells contain so much garbage they cannot function—just as the city of New York cannot function when streets are full of garbage. The death of individual cells progresses to the death of an entire organ, then to the death of the pet.

Death cell by cell
The concept that a pet’s death is caused by cell death is difficult for some to understand. What it means is that a pet’s organs function until so many cells within the organ die that the organ dies. Organ death sets up a domino effect and after one organ dies, so does another. The rate of death can be gradual or it can be rapid. Thus, chronic infections like ehrlichia and Lyme disease kill enough kidney cells that the kidneys fail. As the kidneys fail, the heart, brain, liver, and other organs also begin to die. A pet with a weak heart will die much faster than a pet with a healthy heart, but they both die.

Another example of cell death is what occurs when pets eat contaminated pet food. For example, within the last year or so, pet foods contaminated with aflatoxin mold were sold in the United States. Dogs that ate this food died because aflatoxin damages the cells of the liver. Because the liver contributes to blood clotting, blood sugar regulation, and inflammation that fights cancer, pets that ate very much contaminated food died rapidly. Other pets that consumed smaller amounts of aflatoxin-contaminated food experienced liver cell damage, but they will die more slowly—most with cancer. Aflatoxin is known to cause cancer, perhaps because aflatoxin damages the liver and prevents the liver from participating in the immune system’s attack on cancer cells.

Also in the last year, there have been cats and dogs killed by pet food containing toxic amounts of Vitamin D. Vitamin D, like many nutrients that are beneficial in small amounts, is toxic when present in large amounts. Excess Vitamin D causes cells to retain too much calcium and the calcium ruins the kidneys. These pets die slowly or quickly of kidney failure—depending upon how many healthy kidney cells they had before eating the improperly formulated pet food.

The articles here were answered by a variety of pharmacists and veterinarians   Date Category Topic 09/29/06  Digestive Care  VOMITING (CONT.) 05/22/06  Other  MY 11 MO OLD YORKIE DIED A WEEK AGO 03/05/06  Other  VOMITING 12/30/05  Digestive Care  CAN I GIVE MY DOGS VEGETABLES, FRUITS, RICE? 12/15/05  Pain/Inflammation  CAN I GIVE AN ADVIL? 12/05/05  Other  SEZORS 11/27/05  Seizure Disorder  SIDE EFFECTS PF PHENABARB 10/04/05  Other  NEED TO GET REVOLUTION OFF MY PETS (CATS & DOGS) 05/12/04  First Aid  VET COULDN'T MAKE HIM VOMIT.

 

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