RESUMEN
Lead (Pb) is a ubiquitous environmental pollutant, widely distributed, representing a high toxicological and ecotoxicological risk. Several morphological, functional, and biochemical parameters have been proposed as biomarkers of effect and exposure to Pb. The information related to adverse effects of Pb is not abundant for adult amphibians. These animals are of interest, because during their development they move from aquatic to terrestrial habitats, which may be polluted by the metal since they are receptors of products generated by anthropogenic activities. Previous studies carried out on the adult South American toad Bufo arenarum (Amphibia, Anura) showed that it has a high tolerance to lead and studied the effect of sublethal doses of the metal on the erythrocyte osmotic fragility and delta-ALAD activity. It was also shown that after a single injection of Pb, a significant increase in the number of reticulocytes was produced, suggesting the suitability of those cell counts as a biomarker of exposure to the metal; its impact on the immune system of the toads was also studied. In this work we extend our early studies on the same species evaluating the chronic effect of sublethal Pb (equivalent to 5.6% of the 120-h LD-50) on free erythrocyte protoporphyrin (FEP) and blood Pb and delta-ALAD activity; blood lead was positively associated with a significant decrease in the enzyme activity and to an increase in the FEP level. Pb concentration in target organs (liver, spleen, femur, and kidney) and the total cumulated amount as well as its impact over the mass of those organs were also determined. In addition, the magnitude of the possible depuration through urine and intestine was evaluated. Our results showed that FEP, delta-ALAD, and blood Pb are reliable biosensors of chronic metal intoxication, the former being the marker with the highest sensitivity.
Asunto(s)
Técnicas Biosensibles , Bufo arenarum/sangre , Eritrocitos/efectos de los fármacos , Intoxicación por Plomo/sangre , Compuestos Organometálicos/toxicidad , Contaminantes Químicos del Agua/toxicidad , Animales , Eritrocitos/metabolismo , Masculino , Compuestos Organometálicos/farmacocinética , Porfobilinógeno Sintasa/metabolismo , Protoporfirinas/metabolismo , Sensibilidad y Especificidad , Contaminantes Químicos del Agua/farmacocinéticaRESUMEN
Lead is an element of risk for the environment and human health and has harmful effects that may exceed those of other inorganic toxicants. The immune system is one of the targets of lead. Its immunomodulatory actions depend on the level of exposure, and it has been demonstrated that environmental amounts of the metal alter immune function. Very little information is available regarding the effect of the metal on different aspects of the immune system of lower vertebrates, in particular of amphibians. The aim of this study was to investigate the effect of sublethal lead (as acetate) on the function of polymorphonuclear cells of Bufo arenarum. The results revealed that phagocytic and lytic functions of the adherent blood cells collected from sublethal lead-injected toads and incubated with suspensions of Candida pseudotropicalis were affected negatively. The decrease of the phagocytic activity was correlated with increased blood lead levels (P < 0.0001). Additional information referred to the total and differential leukocyte counts was presented; the only difference found was in the number of blast-like cells that resulted augmented in the samples of lead-injected toads. It was concluded that the evaluation of these parameters might be a reliable tool for the biological monitoring of the immune status of amphibians.
Asunto(s)
Bufo arenarum/sangre , Intoxicación por Plomo/inmunología , Neutrófilos/efectos de los fármacos , Compuestos Organometálicos/toxicidad , Fagocitosis/efectos de los fármacos , Contaminantes Químicos del Agua/toxicidad , Animales , Candida tropicalis/inmunología , Plomo/sangre , Intoxicación por Plomo/fisiopatología , Recuento de Leucocitos , Masculino , Neutrófilos/inmunología , Neutrófilos/microbiología , Fagocitosis/inmunologíaRESUMEN
The aim of the present investigation was to standardize a method for measuring delta-aminolevulinic acid dehydratase (ALAD) activity in circulating red blood cells of adult Bufo arenarum kept in controlled environmental conditions, and to obtain reference basal values suitable for environmental monitoring of lead exposure. The normal ALAD activity for B. arenarum was 131.86 + 14.47 U per liter of red blood cells (n = 38, mean + SEM; interval 72.98 - 263.33). In animals exposed to lead, ALAD activity decreased as lead dose increased.