Effects of lead on gamma-glutamyl transpeptidase and (Na+ -K+)-adenosine triphosphatase of the small intestinal mucosa.
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.
D000818:Animals; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000201:enzymology*; D007421:Intestine, Small / Q000201:enzymology*; D007700:Kinetics; D007855:Lead Poisoning / Q000201:enzymology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005723:gamma-Glutamyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*
D005723:gamma-Glutamyltransferase; D000254:Sodium-Potassium-Exchanging ATPase