Effect of lysophosphatidylcholine on K+ transport in rat heavy gastric membranes enriched with (H+-K+)-ATPase.
K+- and ATP-dependent H+-accumulation in rat heavy gastric membrane vesicles enriched with (H+-K+)-ATPase was markedly stimulated by amphiphiles like lysophosphatidylcholine and Zwittergent 3-14 at concentrations of 10(-5) M. Their stimulatory effect was dependent on K+-concentration in the medium and was abolished by SCH 28,080, a specific inhibitor of (H+-K+)-ATPase. Lysophosphatidylcholine at the optimal dose (3 X 10(-5) M) showed dual effects on K+-dependent membrane functions; it stimulated the rate of K+-uptake by nearly 60%, but partially inhibited SCH 28,080-sensitive and K+-dependent ATP-hydrolysis (about 20% reduction). These data indicate that H+-pumping through (H+-K+)-ATPase in the inside-out gastric membrane vesicles was facilitated by the stimulatory effect of lysophosphatidylcholine on membrane K+-transport in spite of its partial inhibition of ATP-hydrolysis. It appears that the rate limiting step for operation of the ATPase is the availability of K+ ions in the luminal side of the pump. We propose that ionic amphiphiles may modulate K+-transport in rat heavy gastric membranes through specific interactions with the putative K+-transporter.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005753:Gastric Mucosa / Q000378:metabolism*; D007700:Kinetics; D008244:Lysophosphatidylcholines / Q000494:pharmacology*; D008297:Male; D008566:Membranes / Q000201:enzymology; D011188:Potassium / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000032:analysis*; D000644:Quaternary Ammonium Compounds; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism; D013270:Stomach / Q000201:enzymology
D008244:Lysophosphatidylcholines; D000644:Quaternary Ammonium Compounds; C034730:zwittergent 3-12; D006180:Proton-Translocating ATPases; D012413:Rubidium; D011188:Potassium