Intake in Mammals

Lead intake in mammals is caused by both food ingestion and inhaled air containing lead-bearing particles and aerosols. The latter pathway is a two-stage process the deposition of very small lead-bearing materials in the lungs and then the absorption of the metal which ultimately enters the bloodstream. 

In mammals, copper absorption across the intestinal mucosa is inhibited by concomitant high oral intake of zinc (Aaseth and Norseth 1986). In livers from Weddell seals, copper is positively correlated with zinc (Szefer et al. 1994). The addition of zinc to swine diets protects against copper toxicosis caused by eating diets containing 250 mg Cu/kg ration (USEPA 1980). 

The great diversity of terpenes helps to cormteract tolerance by herbivores. In all, terpenes are not very toxic to vertebrates. Many mammals ingest a significant amount of terpenoids with their diet. Monoterpenes from pine oil added to the diet reduces food intake in red deer, Cervuselaphus, calves (Elliot and Loudon, 1987). The brush-tailed possmn, Trichosurus vulpecula, detoxifies (-l-)-a-pinene to alcohol and carboxylic acid derivatives. 

In mammals, muscle breakdown or excess protein intake results in an imbalance between the fates of the carbon chains and the amino nitrogen. Unlike fat (lipid storage) or glycogen (carbohydrate storage), excess amino acids are not stored in polymeric form for later utilization. The carbon chains of amino acids are generally metabolized into tricarboxylic acid (TCA) cycle intermediates, although it is also possible to make ketone bodies such as acetoacetate from some. Conversion to TCA intermediates is easy to see in some instances. For example, alanine is directly transaminated to pyruvate. 

There is no evidence for any toxic effects of chromium(III), which is an essential trace element in mammals (required daily intake 50-200 /tg) and participates in glucose and lipid metabolism. In the low-molecular-weight Cr binding substance (LMWCr), an oligopeptide, a tetranuclear Crm carboxylate complex may be present.44... 

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