Treatment of Pooled Cells without Plasma

The effects of lead, iron, copper, and zinc ions on 8-aminolevulinic acid dehydratase from red blood cell haemolysates in humans, both in the absence and presence of plasma proteins, have been investigated. 8-aminolevulinic acid dehydratase (ALAD) was not found to be a specific indicator of blood lead concentrations since it was also inhibited by copper and activated by zinc. Plasma protein protected the enzyme from both inhibition and activation. ALAD activity was found to be an indicator of the total metal ion concentration in the blood and was therefore considered to be of doubtful value in screening large populations for increased lead absorption. The inhibitory effect of lead on 8-aminolevulinic acid dehydratase (E.C. 4.2.1.24, ALAD) in patients with lead poisoning was first demonstrated by Lichtman and Feldman (1963). Numerous workers (Bonsignore et al., 1965, 1969; Bonsignore, 1966; Nakao et al., 1968) later confirmed these findings. The degree of inhibition has been correlated with blood lead levels (Hernberg et al., 1970; Millar et al., 1972) and these workers showed that even so-called normal levels of lead affected this enzyme. Some workers, however, have found the inhibitory effect of lead on ALAD to be too sensitive to be a useful indication of over exposure to lead (Haeger-Aronsen et al., 1971). There have been conflicting reports regarding the inhibition of ALAD by other inorganic ions (Gibson et al., 1955; Calissano et al., 1965; Abdulla and Haeger-Aronsen, 1971; Lauwerys et al., 1973). It seemed appropriate to investigate the effect, not only of lead but also of zinc, copper, and iron which are normally present in whole blood in humans, and the possible interaction of these ions on ALAD. Such an investigation would be of value in understanding the interrelationship that may exist between these ions in blood. Materials and methods