Conference paper
Potential essentiality of lead
K. Schwarz
; Laboratory of Experimental Metabolic Diseases, Veterans Administration Hospital, Long Beach, California, 90822, and Department of Biological Che¬mistry School of Medicine, University of California, Los Angeles, California
Abstract
Toxicity cannot be used as an argument against the possibility that an element may be essential. An attempt to determine whether or not lead is essential ds therefore being made in our laboratory, using a technique which has been successful in several other cases (tin, vanadium, fluorine, silicon). It consists of the application of ultraclean, more or less trace-element sterile (but not bacteriologically sterile) isolators, and highly purified amino acid diets. All compounds tested are added to the diet. Young rats maintained in the trace-element isolator system develop deficiencies when unidentified essential trace elements are missing from the diet, the most important symptom being lack of growth. Other signs are shagginess of the fur seborrhea, lack of incisor pigmentation, etc. In order to work with lead, an air filter system has been developed which removes not only dust particles, but also aerosols and substances present as vapors. The basal diet contains 53 individual components (21 amino acids, 13 vitamins, sucrose, 2 fats, 3 salts and 13 trace clement compounds). It was difficult to obtain all of these in lead-free form and monitor their lead content. Special problems were encountered with calcium phosphate, certain amino acids and the fats. The basal diet contains approximately 0.2 ppm of the element. In 13 successive experiments, carried out in 1972/73, growth responses were seen when 1.0-2.5 ppm of lead in form of lead subacetate was added to this ration. The growth effects were statistically highly significant, even though they amounted on the average to an increase of less than 20%. Not only lead subacetate but also lead oxide and lead nitrate produced this response. In extended trials aimed at amplifying these initial data we were at first unable to repeat the results. Screening of possible sources of lead in the system showed that extreme caution was indicated. The lead content of plastic bags, used for storing diets, varied greatly, and a labeling tape used for numbering of diets and animal cages contained 0.560/o (56000 ppm) of the element. Elimination of these potential sources of Lead, and continuous monitoring of all plastic components was necessary for the demonstration of the growth promoting effect.
Keywords
Hrčak ID:
167308
URI
Publication date:
6.4.1976.
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