Blood Flow to Various Organs and Tissues

Organ Total Blood Flow (ml/min) Organ Mass (% of body weight) Percent of Heart Output Relative Blood Flow (ml/min/lOOg) Percent Lipid Relative DDT Concentration (mg/kg)  

To do this efficiently, the blood flow through the kidneys must be high in order to filter a lot of blood very quickly. As a result of this high blood flow and the types of activities that occur in these organs, the liver and kidneys are primary sites of chemical storage. 

Fat has low blood flow. For example, five times more blood flows to the skin than to fat reserves (table 6.1). However, many chemicals are stored primarily in fatty tissues because they are lipophilic (fat-loving). For example, the distribution of DDT administered to laboratory rabbits through the diet was examined by chemically analyzing the organs. The results of this study indicated that roughly similar DDT concentrations were found in the brain and fat tissues, even though the brain receives 55 times higher blood flow than fat (table 6.1). 

However, because blood flow to the fat is very low, distribution into fat takes time. Therefore, a chemical like dioxin may first be distributed to the liver, but the amount in the liver will decrease with time as some reenters the blood supply and reaches fat cells. Some will also be metabolized by and interact with the liver, but the dioxin not affected by the liver will likely reach the fat cells. This phenomenon of a chemical having two different destinations over time is known as redistribution. 

In addition to fat, bone is another tissue that has a relatively low blood flow yet still is the preferential storage location for some chemicals, most notably lead and fluoride. In general, chemicals that are stored in bone are elements (e.g., lead and strontium) that bind to the structure of the bone. As with fatty tissue, chemicals bound to bone can be redistributed if bone tissue is lost, such as in osteoporosis. Lead is not toxic to bone however, both fluoride and strontium are. 

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Table 6.1. Blood Flow to Various Organs and Tissues...

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