Interactions of sodium-proton exchange mechanism in dog red blood cells with N-phenylmaleimide.
Dog red blood cells (RBC) have a Na-H exchanger that is reversibly activated by cell shrinkage. The Na-H exchanger can be fixed in the on or off mode by treating the cells with N-phenylmaleimide. This action depends on the volume of the cells at the time of exposure to N-phenylmaleimide and also on the concentration of the reagent per number of cells. If the cells are swollen in hypotonic media during N-phenylmaleimide exposure, the Na-H exchanger becomes irreversibly inactivated, so that on subsequent shrinkage of the cells, no amiloride-sensitive Na flux is seen. This effect is maximal at N-phenylmaleimide concentrations of greater than 20 mumol/g hemoglobin. If the cells are shrunken in hypertonic media during N-phenylmaleimide exposure, the response of the Na-H exchanger depends critically on the concentration of the reagent. At N-phenylmaleimide concentrations of less than 20 mumol/g hemoglobin, the Na-H exchanger is fixed in the activated state, so that even when the volume stimulus is removed by subsequent cell swelling, an amiloride-sensitive flux is seen. Higher concentrations of N-phenylmaleimide applied to shrunken cells inhibit the Na-H exchanger. The results are accounted for in a model that envisions a volume-responsive switching mechanism for Na-H exchange that has two functional groups capable of reacting with N-phenylmaleimide. The accessibility of these groups is determined by cell volume.
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001696:Biomechanical Phenomena; D002352:Carrier Proteins / Q000378:metabolism*; D004285:Dogs / Q000097:blood*; D004912:Erythrocytes / Q000378:metabolism*; D007038:Hypotonic Solutions / Q000378:metabolism; D008301:Maleimides / Q000494:pharmacology*; D017923:Sodium-Hydrogen Exchangers
D002352:Carrier Proteins; D007038:Hypotonic Solutions; D008301:Maleimides; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; C028525:N-phenylmaleimide