Blood lead content in a peri-urban population of the South American toad Bufo arenarum.

Blood Pb concentration in a South American toad Bufo arenarum population (n = 152) was determined over 10 samplings carried out between December 1996 and November 1999. The studied population lived in the surroundings of the La Plata City, the largest industrial-urban setting of the Buenos Aires Province, Argentina. The presence of the metal was detected in all the samples tested, the mean concentration range being 1.99-4.66 mg dl(-1). Some preliminary environmental data on soil content of Pb in the sampling area suggest the anthropogenic origin of the metal possibly due to high rate of Pb-containing gasoline utilisation until recently. The reported results may reflect a sequel of a sustained local air-soil-water pollution process.

Blood lead concentration and delta-aminolevulinic acid dehydratase activity in adult Bufo arenarum.

The effects of sublethal doses of lead (as acetate) on blood parameters of adult male Bufo arenarum were studied. Toads received one single injection with 10, 25, 50 or 100 mg/kg of body weight, equivalent to approximately 1/90-1/10 of the 120 h-LD50; seven days after the injections, the hematocrit and the blood delta-aminolevulinic acid dehydratase (ALAD) activity were measured. Hematocrit of lead-injected animals did not exhibit significant changes respective to controls that received sodium acetate (range 29.8-38.8%). Blood lead concentrations were positively and significantly correlated with the injected metal doses. Blood ALAD activity declined proportionately to the doses of the metal as well as to its whole blood concentration. Because of its sensitivity and specificity, it was concluded that the activity of delta-ALAD may be adopted as a reliable biomarker of Bufo arenarum experimental lead intoxication.

Red blood cell osmotic fragility in Bufo arenarum exposed to lead.

The effects on red blood cells of a single sublethal dose of Pb of 100 mg kg-1 administrated to adult Bufo arenarum were studied. The blood d-aminolevulinic acid dehydratase (d-ALAD) activity, the red blood cell (RBC) osmotic fragility (OF), and the hematocrit (Hct) were measured in control and lead poisoned toad. The enzyme d-ALAD is considered as a specific biomarker for human and animals lead exposure. In Bufo, lead also provoked a significant decrease in the d-ALAD activity without changes in the Hct. OF test was used to compare the impact of Pb on the extent of the RBC hemolysis produced by osmotic stress. Experimental data (absorbance of solubilized hemoglobin and [NaCl]) were fitted to the Orcutt et al. equation (1995) that allows a precise characterization of the parameters involved in OF. In blood from injected toads, the OF resulted significantly reduced. These changes were interpreted as a consequence of alterations in the composition and conformation of the RBC membrane due to Pb, as it was described for human erythrocytes.

Delta-aminolevulinic acid dehydratase (ALAD) activity in blood of Bufo arenarum (Anura).

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 72.98-236.33). In animals exposed to lead, ALAD activity decreased as lead dose increased.