The acute effect of lead acetate on glucocorticoid receptor binding in C6 glioma cells

The in vitro effects of Pb acetate on NO production by C6 glial cells

The CNS neurotoxic effects of lead (Pb) are well documented; however, the molecular toxicity targets have not been clearly delineated. Astroglial cells, which are the most abundant cells in the brain and provide critical support to the neurons, are known to accumulate Pb. Although NO generated by inducible NO synthase (iNOS) in glial cells has been associated with many neurotoxic events, it can also serve to protect by modulating blood flow, increase antimicrobial and tumoricidal activities, and promote immune responses following injury or insult. The present investigations were designed to test the hypothesis that Pb exposure may perturb cytokine signal transduction pathways leading to NO production by astroglial cells. Pretreatment with Pb acetate (500 nM-10 microM) attenuated the generation of NO in a concentration-dependent manner up to 90%, and suppressed iNOS protein expression, as well as interfered with the homeostatic functions of calcium in the cytokine-induced NO signal transduction pathway. In addition, pretreatment with staurosporine, a serine-threonine kinase inhibitor, or KT5720, a specific protein kinase A inhibitor (PKA), inhibited cytokine-induced NO production in a concentration-dependent manner with IC(50) values of 26.3 and 346.7 nM, respectively. Therefore, Pb may impede events within the PKA signal transduction pathway; although, based on results from a gel shift assay, Pb does not directly affect PKA enzyme activity. Taken together, these results suggest the possibility that the suppressive effect of Pb acetate on cytokine-induced NO production in glial cells may be implicated in the neurophysiologic changes noted following occupational or environmental exposure to Pb.

Gestational and lactational lead intoxication produces alterations in the hepatic system of rat pups

The effects of lead (Pb) intoxication during pregnancy and lactation were studied in the hepatic system of pups and young Wistar rats to test the hypothesis that gestational and lactational lead exposure alters the normal function of the liver in neonates. Lead acetate (300 mg/L) dissolved in distilled water was administered ad libitum to mothers during gestation and lactation. At days 12 and 21 postnatal (PN), pups were sacrificed, blood was collected, and livers were removed. Blood lead (PbB) levels were also measured. Although, histological evaluation revealed neither abnormalities in the liver structure nor depositions of lead, the toxicant produced biochemical alterations. Lead-intoxicated pups exhibited a decrease in hemoglobin, iron, and alkaline and acid phosphatase levels and an increase in PbB content. Protein, DNA, and lipid total amounts were reduced, and hepatic glycogen content was diminished at days 12 and 21 PN, with a higher level of glucose in the blood. Lead administration also resulted in a decrease in alkaline phosphatase in the liver of pups at day 21 PN, but acid phosphatase was unaltered. The findings of this study support the hypothesis that lead intoxication of mothers in gestation and lactation results in alterations in the hepatic system in neonates and pups.

Biochemical approaches to studying neurotoxicity

This overview provides an introduction to biochemical analysis of toxicant effects on the nervous system. It includes a brief discussion of the salient features of the nervous system and a review of the various approaches used to detect and identify neurotoxicants and their modes of action.

Influence of lead acetate and selected metal salts on tryptophan binding to rat hepatic nuclei

This study evaluated whether lead acetate or other selected metal salts would influence the binding of L-tryptophan to rat hepatic nuclei. Lead salts and other salts of cadmium, zinc, mercury, and molybdenum, when added alone, had only small effects on 3H-tryptophan binding to hepatic nuclei in vitro. However, each of these salts, when added along with unlabeled L-tryptophan (excess, 10(-4) M), caused significantly less inhibition of 3H-tryptophan binding to hepatic nuclei than did unlabeled L-tryptophan alone. Lead acetate (10(-10) to 10(-4) M), when added along with unlabeled L-tryptophan, abrogated the inhibition of binding related to unlabeled L-tryptophan alone. Sodium arsenite (but not potassium arsenate) as well as sodium selenite (at 10(-4) M concentrations) inhibited to a moderate degree the in vitro 3H-tryptophan binding to hepatic nuclei, but addition of 10(-4) dithiothreitol, a protective agent for sulfhydryl groups, diminished this inhibition. Rats receiving a high dose of lead acetate before being tube-fed L-tryptophan displayed a decrease in hepatic protein synthesis compared with the stimulatory response connected with L-tryptophan alone. Thus, the addition of lead acetate and of other metal salts appears to have an inhibitory effect on L-tryptophan binding to hepatic nuclei. Lead acetate was investigated in in vivo experiments and was found to negate the stimulation of hepatic protein synthesis related to L-tryptophan alone.