β-Adrenergic regulation of constitutive nitric oxide synthase in cardiac myocytes

Abstract

Nitric oxide (NO) has been implicated in endogenous control of myocardial contractility. However, NO release has not yet been demonstrated in cardiac myocytes. Accordingly, endogenous NO production was measured with a porphyrinic microsensor positioned on the surface of individual neonatal or adult rat ventricular myocytes ( n > 6 neonatal and adult cells per experiment). In beating neonatal myocytes, there was no detectable spontaneous NO release with each contraction. However, norepinephrine (NE; 0.25–1 μM) elicited transient NO release from beating neonatal (149 ± 11 to 767 ± 83 nM NO) and noncontracting adult (157 ± 13 to 791 ± 89 nM NO) cells. NO was released by adrenergic agonists with the following rank order of potency: isoproterenol (β1β2) > NE (α/β1) > dobutamine (β1) ≈ epinephrine (α/β1β2) > tertbutylene (β2); NO was not released by phenylephrine (α). NE-evoked NO release was reversibly blocked by N G-monomethyl-l-arginine, trifluoperazine, guanosine 5′- O-(2-thiodiphosphate), and nifedipine but was enhanced by 3-isobutyl-1-methylxanthine (0.5 mM = 14.5 ± 1.6%) and BAY K 8644 (10 μM = 11.9 ± 1%). NO was also released by A-23187 (10 μM = 884 ± 88 nM NO), guanosine 5′- O-(3-thiotriphosphate) (1 μM = 334 ± 56 nM NO), and dibutyryl adenosine 3′,5′-cyclic monophosphate (10–100 μM = 35 ± 9 to 284 ± 49 nM NO) but not by ATP, bradykinin, carbachol, 8-bromoguanosine 3′,5′-cyclic monophosphate, or shear stress. This first functional demonstration of a constitutive NO synthase in cardiac myocytes suggests its regulation by a β-adrenergic signaling pathway and may provide a novel mechanism for the coronary artery vasodilatation and enhanced diastolic relaxation observed with adrenergic stimulation.

Biphasic effect of SIN-1 is reliant upon cardiomyocyte contractile state

“…In our previous publication, FeTPPS (10 μmol/L) alone was shown to have no effect on the cardiomyocyte response to ISO [13]. Additionally, studies have shown that acute β-adrenergic stimulation could alter endogenous nitric oxide production [24,25]. This change in nitric oxide levels could shift the equilibrium of nitric oxide and superoxide produced by SIN-1, potentially changing the level of peroxynitrite production.…”

“…However, upon repetition of the above experimental protocol with the addition of 10 μmol/L FeTPPS, the positive effect of 10 μmol/L SIN-1 on submaximal β-adrenergic stimulation was no longer observed (data not shown). Additionally, since endogenous nitric oxide production has been shown to change during acute β-adrenergic stimulation [24,25], we chose to inhibit endogenous nitric oxide production in another series of functional experiments using the L-arginine analog L-NAME, a non-specific inhibitor of nitric oxide synthase. After reaching steady-state in normal Tyrode control solution and a steady-state response to 0.01 μmol/L ISO, superfusion with 0.01 μmol/ L ISO+10 μmol/L SIN-1 in the presence of 100 μmol/L L-NAME still resulted in a significant increase in myocyte [ Fig.…”

Insulin resistance induces hyperleptinemia, cardiac contractile dysfunction but not cardiac leptin resistance in ventricular myocytes

“…12,4 Constitutive NOS (cNOS) and inducible NOS (iNOS) are both present in ventricular myocytes. 13,14 To examine if NO is involved in the action of leptin in starch and sucrose myocytes, the effect of leptin on PS was reexamined in the presence of the NOS inhibitor L-NAME (100 mM). L-NAME alone had no effect on PS over 30 min (data not shown).…”

Leptin Attenuates Cardiac Contraction in Rat Ventricular Myocytes

“…20 Constitutive NOS and inducible NOS are both present in cardiac myocytes. 21,22 To examine the potential mechanism of action for leptin, the effect of leptin on PS and intracellular Ca 2ϩ transients was reexamined in the presence of the NOS inhibitor L-NAME (100 mol/L). L-NAME alone had no effect on PS and intracellular Ca 2ϩ transients over 30 minutes (data not shown).…”