Biochemical and toxicological response of infant baboons to lead driers in paint.

In an effort to define the toxicology and disposition of lead compounds that presently exist in paint (i.e., organic driers), a controlled dose feeding study was initiated early this year with the use of 28 infant baboons as experimental animals. The infant baboon, established as a metabolic model for a child ingesting lead, will be used to determine the adequacy of present as well as recently recommended limitations for lead in paint to assure protection from this potential source of lead exposure. To accomplish this goal, research has been designed to determine basic dose-response relationships in animals ingesting constant daily doses of a dried paint, a lead octoate drier, and lead acetate. Doses for these compounds have been chosen to cover a broad range of concentrations including that recommended by the American Academy of Pediatrics from the maximum daily permissible lead ingestion, and associated estimates of paint intake by children with pica. PARAMETERS OF METABOLIC RESPONSE FOR EACH LEAD COMPOUND, INCLUDE: general clinical surveillance, lead concentrations in blood, urine and feces, erythrocytic delta-aminolevulinic acid dehydratase and free erythrocytic porphyrin. The response of several of these measures of lead exposure as a function of time will be discussed for each compound at the several dose levels administered.

Measurement of 5-aminolaevulinic acid by reversed phase HPLC and fluorescence detection.

A new method for sensitive measurement of delta-aminolaevulinic acid (ALA) in biological material is described. ALA is derivatized with dansyl chloride, separated by HPLC and estimated using a fluorescence detector. The pretreatment of biological samples includes desamination of L-alpha-aminoacids with L-aminoacid-oxidase before dansylation. The sensitivity of the method is slightly below 1 pmol/injection for standards and the lower limit of quantification is 0.1 mumol/l for plasma and 10 nmol/l for cerebrospinal fluid. Reference values in plasma are 3.53 +/- 1.75 (SD) (n = 43) mumol/l and in packed erythrocytes they ranged from 6 to 26 mumol/l (mean: 14.0 +/- 5.5 mumol/l). In cerebrospinal fluid of non-porphyric individuals less than 2 nmol/l were recovered.

Identification of 2-hydroxy-2-methyllevulinic acid in urine and serum of diabetic patients with ketoacidosis.

A new organic acid, 2-hydroxy-2-methyllevulinic acid, was identified in the urine of four diabetic patients with ketoacidosis using gas chromatography-mass spectrometry. The compound was also detected in two serum samples of the four patients. The compound became undetectable in the urine of the patients after insulin therapy and was not detected in urine and serum of healthy subjects or diabetic patients without ketosis. 2-Hydroxy-2-methyllevulinic acid was also detectable in the urine of a child with elevated blood lactate and pyruvate, and ketosis. This finding suggests that the occurrence of 2-hydroxy-2-methyllevulinic acid is not specific to "diabetic" ketosis but is correlated to ketosis itself.

Erythrocyte delta-aminolaevulinic acid dehydratase activity and changes in delta-aminolaevulinic acid concentration in various forms of anaemia.

Whole blood delta-aminolaevulinic acid (ALA) concentrations and erythrocyte ALA dehydratase activity have been measured in patients with iron deficiency anaemia, megaloblastic anaemia and secondary anaemia, and in normal subjects. ALA concentration was found to be significantly increased in all types of anaemia compared with normal. Erythrocyte ALA dehydratase activity was significantly increased in iron deficiency and megaloblastic anaemia but not in secondary anaemia.

Lead and zinc poisoning and the interaction between Pb and Zn poisoning in the foal.

Groups of young growing horses were fed toxic amounts of lead only, zinc only and the same amounts of lead and zinc together. Those fed Pb only developed pharyngeal and laryngeal paralysis ("roaring") whereas those fed Zn only and Pb and Zn together developed the same clinical syndrome which included swelling at the epiphyseal region of the long bones, stiffness and lameness. Anemia and decreased weight gains were most pronounced in animals fed Zn for the longest periods. Animals fed Pb only did not become anemic and weight loss did not occur until after there was an interference in swallowing. The clinical signs and tissue Pb values from animals fed toxic amounts of both Pb and Zn continuously, differed markedly from those present in animals fed comparable amounts of Pb only. Th clinical signs were similar to those caused by Zn poisoning. The hepatic and renal tissue Pb values were approximately twice as high and the epiphyseal and cancellous bone sample results were one half as high as the comparable Pb values from animals fed toxic amounts of Pb only. It appeared that toxic amounts of Zn prevented the development of clinical signs of Pb poisoning in the young growing horse.

Repression of the overproduction of porphyrin precursors in acute intermittent porphyria by intravenous infusions of hematin.

In a patient with a severe attack of acute intermittent porphyria, hematin given intravenously caused marked diminution of serum delta-aminolevulinic acid and porphobilinogen. The decline of aminolevulinate was more rapid than that of porphobilinoge. After 2 days of hematin administration, about 5 days were required for delta-aminolevulinic acid, and 11 days for porphobilinogen to return to the concentrations that were detected before treatment. Urinary excretion of both compounds also decreased after hematin administration. Considerable amounts of porphobilinogen were also found in the cerebrospinal fluid of the patient.