The activity of membrane enzymes in homogenate fractions of rat kidney after administration of lead

Rats received one or two consecutive daily ip injections, each 0.5 mg Pb 2+/100 g body weight, and the kidneys were studied 48 or 24 hr, respectively, after the injection. Renal brush border preparations from Pb 2+-treated rats exhibited significant decreases in the activity of alanine aminopeptidase and γ-glutamyl transpeptidase, greater after two injections, yet the amount of brush border protein remained unchanged. Moreover, the activity of alkaline phosphatase in the brush border was significantly increased after Pb 2+. No significant changes in urine volume, urinary protein, or enzymes could be detected in these experiments. The enzymatic changes observed in the brush border after acute exposure to Pb 2+ contrasted with those after exposure to Hg 2+ where both the structure and enzymatic functions were severely damaged and after exposure to Cd 2+ where enzymatic alterations were not accompanied by cytological changes.