NADH supplementation decreases pinacidil-primed I K ATP in ventricular cardiomyocytes by increasing intracellular ATP.
1 The aim of this study was to investigate the effect of nicotinamide-adenine dinucleotide (NADH) supplementation on the metabolic condition of isolated guinea-pig ventricular cardiomyocytes. The pinacidil-primed ATP-dependent potassium current I(K(ATP)) was used as an indicator of subsarcolemmal ATP concentration and intracellular adenine nucleotide contents were measured. 2 Membrane currents were studied using the patch-clamp technique in the whole-cell recording mode at 36-37 degrees C. Adenine nucleotides were determined by HPLC. 3 Under physiological conditions (4.3 mM ATP in the pipette solution, ATP(i)) I(K(ATP)) did not contribute to basal electrical activity. 4 The ATP-dependent potassium (K((ATP))) channel opener pinacidil activated I(K(ATP)) dependent on [ATP](i) showing a significantly more pronounced activation at lower (1 mM) [ATP](i). 5 Supplementation of cardiomyocytes with 300 micro g ml(-1) NADH (4-6 h) resulted in a significantly reduced I(K(ATP)) activation by pinacidil compared to control cells. The current density was 13.8+/-3.78 (n=6) versus 28.9+/-3.38 pA pF(-1) (n=19; P<0.05). 6 Equimolar amounts of the related compounds nicotinamide and NAD(+) did not achieve a similar effect like NADH. 7 Measurement of adenine nucleotides by HPLC revealed a significant increase in intracellular ATP (NADH supplementation: 45.6+/-1.88 nmol mg(-1) protein versus control: 35.4+/-2.57 nmol mg(-1) protein, P<0.000005). 8 These data show that supplementation of guinea-pig ventricular cardiomyocytes with NADH results in a decreased activation of I(K(ATP)) by pinacidil compared to control myocytes, indicating a higher subsarcolemmal ATP concentration. 9 Analysis of intracellular adenine nucleotides by HPLC confirmed the significant increase in ATP.
Pelzmann
Brigitte
B
Institut für Medizinische Physik und Biophysik, Karl-Franzens-Universität Graz, Harrachgasse 21, A-8010 Graz, Austria.
Hallström
Seth
S
Schaffer
Peter
P
Lang
Petra
P
Nadlinger
Karl
K
Birkmayer
George D
GD
Vrecko
Karoline
K
Reibnegger
Gilbert
G
Koidl
Bernd
B
D000200:Action Potentials; D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005905:Glyburide / Q000493:pharmacokinetics; D006168:Guinea Pigs; D006352:Heart Ventricles; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D009243:NAD / Q000493:pharmacokinetics* / Q000502:physiology*; D018408:Patch-Clamp Techniques; D020110:Pinacidil / Q000008:administration & dosage / Q000037:antagonists & inhibitors* / Q000493:pharmacokinetics*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D012508:Sarcolemma / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology
D015221:Potassium Channels; D009243:NAD; D020110:Pinacidil; D000255:Adenosine Triphosphate; D005905:Glyburide