Ontogenetic dynamics of delta-amino-laevulinic acid dehydratase activity in chick embryo organs and the changes in hepatocytes after exposure to lead.

1. The activity of delta-aminolaevulinic acid dehydratase (ALAD [EC 4.2.1.24]) was determined in the liver, myocardium, distal proximity muscle and yolk sac membrane of chicken embryos at 7, 10, 13, 16, 19, 21 and 22 d of age. 2. Maximum ALAD activity was found in the liver on the 10th day, in the myocardium on the 13th day, in the muscle on the 10th day and in the yolk sac membrane on the 19th day. 3. Exposure of hepatocytes cultured in vitro to different concentrations of lead chloride for 1 h showed that maximum inhibition of ALAD activity occurred with 10 and 50 mg Pb/l. 4. Scanning electron microscopy revealed changes in the surface structure of hepatocytes exposed to 10 mg Pb/l.