Effects of lead and a low-molecular-weight endogenous plasma inhibitor on the kinetics of sodium-potassium-activated adenosine triphosphatase and potassium-activated p-nitrophenylphosphatase.
1. Lead, ouabain and an endogenous plasma inhibitor were all found to be potent inhibitors of purified hog cerebral cortex sodium-potassium-activated adenosine triphosphatase and potassium-stimulated p-nitrophenyl-phosphatase. 2. The kinetic characteristics of inhibition of both enzymes by lead and the endogenous plasma inhibitor differed in several respects. For sodium-potassium-activated adenosine triphosphatase, lead and the endogenous plasma inhibitor were non-competitive inhibitors with respect to potassium; lead was competitive with respect to sodium, whereas the endogenous plasma inhibitor had no effect; lead was competitive with respect to magnesium adenosine triphosphate, whereas the endogenous plasma inhibitor was uncompetitive. For potassium-activated p-nitrophenylphosphatase, both lead and the endogenous plasma inhibitor were competitive with respect to potassium; lead showed a mixed type of inhibition with respect to p-nitrophenylphosphate, whereas the endogenous plasma inhibitor was non-competitive. 3. Lead and the endogenous plasma inhibitor exhibited synergistic inhibitory activity on sodium-potassium-activated adenosine triphosphatase. 4. These results suggest that lead could play a contributory role in the pathogenesis of essential hypertension via an additive inhibition of vascular smooth muscle sodium-potassium-activated adenosine triphosphatase.
Weiler
E
E
Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048.
Khalil-Manesh
F
F
Gonick
H C
HC
D009597:4-Nitrophenylphosphatase / Q000037:antagonists & inhibitors*; D000328:Adult; D001667:Binding, Competitive; D004357:Drug Synergism; D006801:Humans; D007700:Kinetics; D007854:Lead / Q000494:pharmacology*; D008970:Molecular Weight; D045283:Natriuretic Agents / Q000494:pharmacology*; D010042:Ouabain / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors*; D011188:Potassium / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
D045283:Natriuretic Agents; D007854:Lead; D010042:Ouabain; D010744:Phosphoric Monoester Hydrolases; D009597:4-Nitrophenylphosphatase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium