Effects of lead on gamma-glutamyl transpeptidase and (Na+ -K+) -adenosine triphosphatase of the small intestinal mucosa
Wapnir, R.A.; Goldstein, L.; Moak, S.A.
Journal of Environmental Pathology Toxicology and Oncology Official Organ of the International Society for Environmental Toxicology and Cancer 5(4-5): 101-107
1984
ISSN/ISBN: 0731-8898 PMID: 6151594 Document Number: 223879
Oral lead, when fed to young rats for 6 weeks, at a level of 0.50 in the diet, produced an increase in small intestinal mucosal gamma-glutamyl transpeptidase, an enzyme capable of catalyzing membrane translocation of amino acids and small peptides. However, a non-competitive inhibition with the glutamate acceptor used, glycylglycine, was demonstrated for lead, in vitro (l50 = 1.0 mM in purified brush border preparations). Lead ingestion caused a reduction of small intestinal mucosal (Na+ -K+)-ATPase (l50 = 0.4 - 0.6mM). At 0.2 mM concentration, lead was a competitive inhibitor for ATP in a (Na+ -K+)-ATPase assay system in vitro. A higher concentration of lead (0.5 mM) also produced an inhibitory, but non-competitive effect, with a decline of Vmax from 36.6 to 8.1 nmoles/min X cm.