Electrically neutral Na+-H+ exchange in endosomes obtained from rabbit renal cortex.
Endocytotic vesicles (i.e., endosomes) were prepared from rabbit renal cortex following the intravenous injection of horseradish peroxidase. The endosomal population was derived from a 100,000-g pellet and was found at equilibrium in the lightest area of a sucrose density gradient. This population was separate from other organelles as determined by enzyme markers and had a 2.5-fold enrichment of horseradish peroxidase specific activity compared with the homogenate specific activity corrected for soluble horseradish peroxidase activity. The endosomes contain an oligomycin-insensitive, electrogenic H+-translocating ATPase. They also contain an electroneutral Na+-H+ exchanger. This exchanger is not inhibited by amiloride, and lithium is not a substrate for the exchanger. Lithium does inhibit the Na+-H+ exchanger when added prior to the addition of sodium. The Michaelis constant for sodium of the endosomal Na+-H+ exchanger was found to be 10.0 mM. These data indicate that a population of endosomes from rabbit renal cortex contain an electrogenic H+-ATPase and an electroneutral Na+-H+ exchanger and that the exchanger is distinct from the brush-border membrane Na+-H+ antiporter.
D000818:Animals; D004563:Electrochemistry; D005260:Female; D006859:Hydrogen / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism*; D007474:Ion Exchange; D007672:Kidney Cortex / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism; D009940:Organoids / Q000201:enzymology; D011522:Protons; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*
D011522:Protons; D006859:Hydrogen; D012964:Sodium