Liver toxicity due to 1,2-dichloropropane in the rat.

The effect of 1,2-dichloropropane on rat liver was studied after short (5 days) and long term (4 weeks) i.p. administration. Animals were injected daily with 10-500 mg/kg body wt 1,2-dichloropropane and biochemical and histological changes of liver were investigated. Treatment was monitored by measuring urinary mercapturic acid excretion. A significant increase of mercapturate excretion was observed at all dose levels, with no further increase during the treatment; at lower doses a return to baseline values occurred within 48 h after the end of treatment. Mercapturate excretion at the end of weeks 2, 3 and 4 of treatment was significantly lower than that observed at the end of week 1. The liver reduced glutathione content was different after single or repeated injections. A dose-dependent decrease of liver reduced glutathione was observed after a single injection and a dose-dependent increase after 4 weeks. The liver biochemical pattern after 4 weeks of treatment (characterized by a decrease of cytochrome P-450 and by an increase of reduced glutathione and glutathione S-transferase activity) suggests a hyperplastic evolution of the liver cells, probably a repair mechanism induced by early depletion of reduced glutathione. Light microscopy confirms that the prevalent alterations are regenerative in type (atypical mitosis and hyperplastic nodules). Areas of focal necrosis are isolated, and trend to disappear after long term treatment.

Heating reactivation of rats aminolevulinic acid dehydratase in lead poisoning.

Heat reactivation (60 degrees C for 5 minutes) of the red blood cells aminolevulinic acid dehydratase activity was studied in lead treated rats (0.25 to 5.0 mg/kg b.w., i.p., for 4 weeks). Complete enzyme reactivation occurs with lead blood concentration up to about 70 mcg/dl. At higher blood lead concentrations, only a part of the enzyme can be restored by heating. The different mechanisms of aminolevulinic acid dehydratase activity inhibition by lead are discussed.

In vivo interaction of lead with aminolevulinic acid dehydratase and induction of a thermolabile factor: an experimental model.

Aminolevulinic acid dehydratase (ALA-D) activity of male albino Wistar rats was used as an experimental model for a study on the interaction of lead with biological systems. Lead at 1 mg/kg was administered i.p. and the rats were killed immediately, and at 30 min, 1, 2, 3, and 4 h after treatment. It was shown that lead (Pb) interacted directly with the enzyme molecule immediately after treatment, first on the active site of zinc (Zn) and then on the thiolic groups. Induction of the so-called thermolabile factor (TF) seemed to occur later, i.e., it may only be shown from the 2nd-3rd h after treatment. The long-term persistence of lead-induced TF in the acute phase of intoxication may be the key to the interpretation of some chronic toxic effects.

[Evaluation of exposure and of the biological effects in galvanic chromium plating by different technologies]. / Valutazione dell'esposizione e degli effetti biologici nella cromatura galvanica a diversa tecnologia.

In the hard electroplating process, chromium exposure is heavier than in the bright process. The average urinary chromium was 9,7 +/- 7,2 micrograms/g cr. in the 31 bright plating subjects; comparing only the chromium bath workers of the two process, the difference was statistically significant (13,0 +/- 7,5 micrograms/g cr. against 7,6 +/- 4,4 micrograms/g cr. t = 2,4; p less than 0,0025). In a control group composed of 22 sanitary workers, the average urinary chromium was 1,9 +/- 1,4 micrograms/g cr. We found chromium rhinopathy in 40% of the hard process subjects and in 20% of the bright process subjects. Sputum cytologic examination was not correlated with the chromium level exposure. In the exposed workers we found 37% insufficient specimens and 53% metaplasia plus dysplasia; in the 42 control subjects we found 64% insufficient specimens, 33% metaplasia and no dysplasia.

The ceramics industry and lead poisoning. Lead poisoning in relation to technology and jobs.

The investigation evaluates the risk of lead absorption for 288 ceramics industry workers. Cases were studied in relation to sex, type and length of exposure, production plant characteristics, and jobs performed. The difference linked with sex was amplified by the fact that men usually performed the decidedly higher risk jobs, such as those connected with the direct use of ceramic glazes, in which--although to a variable extent--high percentages of lead are used. In fact, decreasing amounts of lead absorption were found for workers engaged in the operations of glazing, kiln work, maintenance and decoration, selection coming last. It was concluded that, in the Italian ceramics industry, lead exposure is linked to the use of lead-rich glazes and that this exposure may thus vary according to the different jobs or different technological cycles. Although female workers primarily carry out decoration and selection jobs, they nonetheless show high levels of lead in their blood, exceeding 1.9 mu mol/l--the limit currently recommended for women.

Site of action of metals on the aminolevulinic acid dehydratase of human erythrocytes.

The site of action of four metals (copper, lead, nickel and zinc) on the aminolevulinic acid dehydratase of human erythrocytes was studied. Data obtained after denaturation of allosteric sites with heat treatment and after simultaneous incubation with two metals suggest the following conclusions: copper acts on the catalytic site, whereas lead, nickel and zinc act on the allosteric sites; zinc and nickel act on the same allosteric (metallic) site; zinc and lead only partially act on the same metallic site; nickel and lead act on different allosteric sites.

[Remarks on the use of shortened procedures in evaluating EDTA-induced urinary lead excretion]. / Sull'impiego di procedimenti abbreviati nell prova di piomburia provocata

Urinary lead excretion following EDTA administration was studied in 47 both normal and lead intoxicated subjects, mainly monitoring the rate of excretion through sequential urine samples. Urinary lead excretion patterns proved to be quite different in the examined subjects: in particular, great differences were noted in the onset of lead excretion increase. The six-hr lead excretion resulted to be 60,7% of the total 24-hr excretion, with, however, a very wide range (42% to 83%). Urine flow didn't appear to influence the rhythm of urinary lead excretion. There is sufficient evidence to justify the conclusion that evaluation of EDTA-induced urinary lead excretion on the basis of the first-six-hr results cannot be assumed as a reliable procedure, unless it is used for rough diagnostic screening purposes.