Possible Interaction: Adenosine and Omega-N-Methylarginine

“We have previously demonstrated that CFR to adenosine was significantly increased after systemic infusion of L-NMMA in normal volunteers but not in recently transplanted denervated hearts.”

“In a separate series of experiments, MBF during adenosine was reduced in the presence of l-NMMA (p < 0.05 analysis of variance).”

“This was most apparent at the low dose of adenosine, where MBF response to adenosine was blunted in the presence of l-NMMA (2.08 +/- 1.34 ml/min/g vs. 1.48 +/- 1.32 ml/min/g, placebo vs. l-NMMA, p < 0.05).”

“The addition of the NO synthase competitive inhibitor, NG-monomethyl-L-arginine (NMMA), or the adenosine receptor antagonist, theophylline, prevented the increase in NO production by adenosine.”

“Furthermore, infusion of NG-monomethyl-L-arginine (L-NMMA) blunted vasodilator responses to Ado infusion only in Ado responders (P < 0.01 vs. post-L-NMMA) and had no effect on exercise in either group.”

“… adenosine flow … ( L-NMMA ) requires inhibition of CNS neuronal nitric oxide synthase (nNOS), increased cardiac sympathetic nerve stimulation, and β2-agonism of coronary arterioles because (1) heart … raise arterial pressure to levels equivalent to those given L-NMMA plus adenosine also did not show increased myocardial blood flow (MBF).”

“RBF during combined infusion of L-NMMA and adenosine was not different from that during adenosine alone, but the decrease in renal vascular resistance was less pronounced during this combination.”

“ L-NMMA blunted the effect of adenosine on cGMP both in unstimulated samples and in aggregated platelets without any effect on cAMP synthesis.”

“ Adenosine increased coronary blood flow before and after L-NMMA (+399.5 +/- 27.5% and +511.9 +/- 33.3%, respectively).”

“Before infusion of L-NMMA, adenosine caused a dose-dependent increase in FBF from 2.3 to 15.9 mL.min-1.dL-1.”

“During concurrent infusion of L-NMMA, adenosine increased FBF from 1.7 to 10.0 mL.min-1.dL-1, and this change from baseline was significantly reduced compared with that before L-NMMA (P < .05).”

“ L-NMMA also attenuated the FBF response to adenosine when the basal constrictor effect of L-NMMA was prevented by coinfusion of the NO donor sodium nitroprusside (n = 6, P < .01).”

“ Adenosine applied via pressurized micropipettes directly onto the wall or at a distance of 25 µm from the wall of first-order … diameter = 54 ± 1 µm) elicited dose-dependent dilations of 15–46% that were significantly reduced by the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA, …–4M).”