Identification and regulation of the gastric H+/K+-ATPase in the rat heart.
Previous reports indicate that H+/K+-adenosine triphosphatase (ATPase) might be expressed in the heart.


OBJECTIVE
The objectives of the present study were to explore the presence of H+/K+-ATPase protein and gene expression in the rat heart and to investigate whether the enzyme could contribute to potassium transport across the sarcolemma.


RESULTS
We performed reverse transcription-polymerase chain reaction (RT-PCR) on mRNA from myocardium and isolated cardiomyocytes using primers specific for the gastric H+/K+-ATPase alpha-subunit. The PCR products were sequenced and the predicted gastric H+/K+-ATPase sequence was verified. Western blots from myocardium detected a 34-kDa band and a 94-kDa band, indicating the beta-subunit and alpha-subunit of the gastric H+/K+-ATPase, respectively. Immunocytochemistry detected significant immunoreactivity of the beta-subunit in cardiomyocytes. H+/K+-ATPase-dependent potassium transport was assessed by 86Rb+-uptake in isolated cardiomyocytes. Both ouabain and the selective H+/K+-ATPase inhibitor Schering 28080 reduced 86Rb+-uptake at maximum specific inhibition, by 70 and 25%, respectively; the effects were additive. Competitive RT-PCR analysis indicated a significant upregulation of the myocardial H+/K+-ATPase in heart failure after myocardial infarction.


CONCLUSIONS
The gastric isoform of H+/K+-ATPase is expressed in rat cardiac myocytes, both at transcript and protein levels. Functional studies indicate that the enzyme could contribute to potassium and pHi regulation in cardiomyocytes.
Beisvag
V
V
Department of Circulation and Medical Imaging, Faculty of Medicine, The Norwegian University of Science and Technology, Trondheim, Norway.
Falck
G
G
Loennechen
J P
JP
Qvigstad
G
G
Jynge
P
P
Skomedal
T
T
Osnes
J-B
JB
Sandvik
A K
AK
Ellingsen
Ø
Ø
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D000818:Animals; D001692:Biological Transport / Q000235:genetics; D015153:Blotting, Western / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000235:genetics*; D017506:H(+)-K(+)-Exchanging ATPase / Q000235:genetics*; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D007093:Imidazoles / Q000494:pharmacology; D007150:Immunohistochemistry / Q000379:methods; D009203:Myocardial Infarction / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012414:Rubidium Radioisotopes; D015854:Up-Regulation / Q000235:genetics
D004791:Enzyme Inhibitors; D007093:Imidazoles; D012333:RNA, Messenger; D012414:Rubidium Radioisotopes; C035235:Sch 28080; D010042:Ouabain; D000251:Adenosine Triphosphatases; D017506:H(+)-K(+)-Exchanging ATPase