Hypertrophied rat heart. New Na+, K+-ATPase-ouabain interactions in sarcolemma vesicles.
The interactions between ouabain and sarcolemmal-bound Na+, K+-ATPase activity have been studied in rat left ventricles 70-130% hypertrophied by aortic constriction. Isolated sarcolemmal vesicles were 75-fold enriched in Na+, K+-ATPase and consisted in both impermeable inside-out vesicles and leaky material. The enzymatic activity was found to be almost completely inhibited at 10(-6) M ouabain instead of 2 X 10(-4) M in the normal left ventricle. In contrast with normal heart in which a Ca2+-free perfusion revealed a Na+, K+-ATPase activity highly sensitive to ouabain, in hypertrophied heart, a pretreatment plus or minus Ca2+ did not affect the high sensitivity form (half maximum inhibition with 0.8-2.2 X 10(-9) M ouabain). This enzyme form differed from the usual Na+, K+-ATPase activities by the absence of any detectable ouabain/K+ antagonism. The levels of 3H-ouabain binding, however, did not correlate with the levels of Na+, K+-ATPase inhibition. These results suggested that the Na+, K+-ATPase-ouabain interactions were altered in hypertrophied rat heart.
D000818:Animals; D001665:Binding Sites; D006332:Cardiomegaly / Q000209:etiology / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000201:enzymology; D010042:Ouabain / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012508:Sarcolemma / Q000201:enzymology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism
D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase