The effect of lead on total globin and alpha- and beta-chain synthesis; in vitro and in vivo

Effect of heavy metal exposure on blood haemoglobin concentration and methemoglobin percentage in Lumbricus terrestris

The earthworm haemoglobin (Hb) is a large extracellular hemoprotein flowing in a closed circulatory system. In spite of the fundamental role of this respiratory pigment in earthworm physiology, little is known about its sensitivity to environmental pollutants. The aim of the present work was to investigate the possible effect of heavy metal (cadmium, copper, mercury) exposure on Hb concentration and oxidation state (methemoglobin formation) in the earthworm Lumbricus terrestris. In addition, the tissue concentration of metallothioneins, a well-known biomarker of heavy metal exposure, was determined as an indicator of metal uptake. The animals were exposed to increasing concentrations of Cd, Cu and Hg utilizing the standard acute toxicity test, "Filter paper test" for 48 h. Exposure to heavy metals (10(-5)-10(-3) M for Cd, 10(-4)-10(-3) M for Hg, and 10(-4)-10(-2) M for Cu) was found to increase haemoglobin concentration in L. terrestris, although the magnitude of such an increase was dependent on the metal. In addition, metal exposure led to the formation of methemoglobin. Compared to other known biological responses to heavy metals, such as metallothionein induction, methemoglobin increase showed a higher sensitivity and a higher percentage variation in exposed organisms, showing to be a possible suitable biomarker of exposure/effect to be included in a multi biomarker strategy in earthworm in soil monitoring assessment.

Hemolytic anemia associated with lead poisoning from shotgun pellets and the response to Succimer treatment

Symptomatic lead poisoning with severe hemolytic anemia was observed in a patient with retained shot gun pellets. Surgical resection of the retained pellets and the use of a newer chelating agent, Succimer (2,3-dimercaptosuccinic acid) successfully lowered blood lead level. Hemolytic anemia was associated with deficient erythrocyte pyrimidine 5'-nucleotidase, and lowering of the lead level corrected the deficiency, suggesting that the enzyme deficiency is responsible for the hemolysis associated with lead poisoning. This case illustrates that retained lead pellets from shotgun wounds can cause severe lead poisoning.

Lead poisoning: clinical, biochemical, and haematological aspects of a recent outbreak

The clinical, biochemical, and haematological aspects of a recent outbreak of lead poisoning, in which exposure was related to the oxyacetylene cutting of red lead painted ironwork, were investigated. Initial suspicion was raised when a blood film showed punctate basophilia which remains a simple and useful method of picking up lead toxicity. Estimations of blood lead concentration and conventional laboratory data confirmed the diagnosis. Although there was prominent punctate basophilia, spectrophotometric analysis showed only negligible accumulation of pyrimidine-5'-nucleotides despite severe suppression of pyrimidine-5'-nucleotidase activity. The pattern of the red cell glycolytic intermediates, investigated for the first time, suggested that lead may also affect glycolysis at the hexokinase step. Once the diagnosis was made intravenous chelation treatment was begun with a rapid improvement in symptoms. Long term follow up is required to assess any sequelae of intoxication. These cases emphasise the classic features of lead poisoning, and despite the currently available diagnostic tests, lead intoxication may still go unrecognised unless a thorough occupational history is taken.

Effect of lead and ethanol upon gamma-globin synthesis in sickle reticulocytes

There is evidence from both in vivo and in vitro studies that the synthesis of hemoglobin can be modified by posttranslational alterations in the assembly of the tetrameric molecule. Globin biosynthesis in reticulocytes of patients with sickle cell disease was studied to ascertain the effects of lead and ethanol on gamma-globin chain synthesis and hemoglobin assembly. In incubations containing lead (400 micrograms/dl) or ethanol (1.0 M) there were 86.7 +/- 139.7% and 542.7 +/- 397.0% increases in the relative synthesis of the gamma-globin chain. This was associated with a relative reduction in alpha-chain synthesis, as estimated by changes in the alpha/gamma + beta S synthesis ratio, as well as a marked reduction in total globin synthesis.

High affinity of lead for fetal haemoglobin

In-vitro experiments using 203Pb were performed to identify lead-binding components in human haemoglobin. Sephadex A-50 ion-exchange chromatography of haemolysate showed that different types of haemoglobin had different affinities for lead. For the haemolysate from adults, lead was present in both Hb A (alpha 2 beta 2) and Hb A2 (alpha 2 delta 2), whereas, in the haemolysate from new-born infants, the haemoglobin of fetal origin, Hb F (alpha 2 gamma 2) showed a much greater affinity for 203Pb than the adult haemoglobin Hb A (alpha 2 beta 2), obtained from maternal blood. Analysis of the 203 Pb-labelled haemoglobin suggested that about 82% of 203Pb was in the globin polypeptide. Further analysis with carboxylmethyl (CM) cellulose chromatography indicated that the gamma globin of fetal origin had a higher affinity for 203Pb than the beta globin, whereas alpha globin appeared to be unimportant in lead binding. The results of the different affinities for lead of different Hb types are discussed with regard to the effect of lead upon haemoglobin synthesis.

A role of red cell pyrimidine 5'-nucleotidase in experimental lead poisoning

Intravenous administration of lead acetate to rabbits for 10 weeks at 2 week intervals resulted in significantly elevated blood lead levels, slight anemia with marked microspherocytosis and moderate basophilic stippling, and marked depression of red cell delta-aminolevulinic acid (ALA) dehydratase activity. However the decrease in red cell pyrimidine 5'-nucleotidase (P5N) activity was slight when compared to the red cell P5N activity of comparable reticulocyte-rich blood, and intracellular accumulation of pyrimidine nucleotides could not be demonstrated. In the in vitro inhibition test the same degree of inhibition of red cell P5N activity seen in hereditary red cell P5N deficiency was obtained by using a lead concentration 200--400 times higher than the lead levels detected in human plumbism. Most importantly, there were no differences in the lead-induced inhibition of human and rabbit red cell P5N. From the results of the in vitro inhibition test, lead-induced red cell P5N deficiency appears to be one of several pathogenic mechanisms in chronic lead exposure associated with the accumulation of lead in bone marrow. A decrease in rec cell P5N activity could not be demonstrated despite the marked depression in red cell ALA dehydratase activity, and slight anemia with marked microspherocytosis and moderate basophilic stippling in this experiment. These results suggest that lead affects red cells at multiple metabolic loci.

Alpha-thalassemia

The current concepts of alpha-thalassemia including incidence, genetics, clinical spectrum and diagnosis are reviewed. Speculation concerning clinical application of the molecular biology of alpha-thalassemia is also presented.

Haemopoietic progenitor cells in prenatal congenitally anaemic 'flexed-tailed' (f/f) mice

The incidences of erythroid colony forming cells (CFUe) and granulocyte-macrophage colony forming cells (CFUc) have been measured in 11-18 d prenatal livers of mice of genotype f/f and nearly congenic +/+ controls. In normal fetal livers numbers of CFUe (cells able to form colonies of 16 or more cells after 72 h in vitro) rise to a maximum on day 14 of gestation and represent c 1% of total fetal liver cells. In f/f fetal livers, peak values for numbers and proportions of CFUe are 50% of normal. The f/f lesion does not reduce the numbers of CFUc in fetal liver. Since this deficiency in CFUe parallels deficiencies of similar magnitude in spleen-colony forming units (CFUs) and erythroblasts in the liver, and erythrocytes in the blood, of f/f fetuses it is concluded that the f/f lesion is expressed at an early stage of haemopoietic development in prenatal life. The possibility that restricted haem synthesis is the primary effect of the f/f genotype and responsible for disturbances of both haemopoietic cellular proliferation and haemoglobin synthesis is examined.