Effects of palmitoyl carnitine and LPC on cardiac sarcolemmal Na+-K+-ATPase.
We have previously reported that palmitoyl carnitine is a potent inhibitor of Na+-K+-ATPase. Recently, Owens et al. [Am. J. Physiol. 242 (Heart Circ. Physiol. 11): H456-H461, 1983] reported that palmitoyl carnitine did not inhibit Na+-K+-ATPase activity of their cardiac sarcolemmal preparation that had been isolated without the use of detergents. We have investigated this using a similar preparation. Palmitoyl carnitine appears to be a much less effective inhibitor of the sarcolemmal preparation at lower concentrations because it simultaneously stimulates Na+-K+-ATPase by unmasking latent activity. When this latent activity is exposed by pretreatment with sodium dodecyl sulfate, a marked inhibition by palmitoyl carnitine is then observed. Similar results were obtained with lysophosphatidylcholine (LPC). The concentrations of palmitoyl carnitine and LPC required to inhibit Na+-K+-ATPase are, however, higher than those that cause sarcolemmal permeability changes; consequently, it is improbable that inhibition of the enzyme by these metabolites occurs to any significant extent in vivo.
D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives*; D004285:Dogs; D008244:Lysophosphatidylcholines / Q000494:pharmacology*; D009206:Myocardium / Q000201:enzymology* / Q000648:ultrastructure; D010172:Palmitoylcarnitine / Q000494:pharmacology*; D012508:Sarcolemma / Q000187:drug effects / Q000201:enzymology; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism
D008244:Lysophosphatidylcholines; D010172:Palmitoylcarnitine; D012967:Sodium Dodecyl Sulfate; D000254:Sodium-Potassium-Exchanging ATPase; D002331:Carnitine