Possible participation of nitric oxide in the increase of norepinephrine release caused by angiotensin peptides in rat atria.
In rat atria isolated with their cardioaccelerans nerves and labeled with [3H]norepinephrine, exposure to 1 x 10(-7) mol/L angiotensin II (Ang II) and 1 x 10(-7) mol/L Ang-(1-7) increased the release of radioactivity elicited by nerve stimulation (0.5-millisecond-long square-wave pulses at 2 Hz during 2 minutes) by 90% and 60%, respectively. The facilitatory effect on noradrenergic neurotransmission caused by both peptides was stereospecifically prevented by N omega-nitro-L-arginine methyl ester (1 x 10(-4) mol/L), an inhibitor of nitric oxide synthase that catalyzes the conversion of L-arginine to nitric oxide, as well as by 1 x 10(-5) mol/L methylene blue, a substance that inhibits the guanylate cyclase considered as the final target of nitric oxide action. On the other hand, the precursor of nitric oxide synthesis. L-arginine (1 x 10(-3) mol/L), reversed the prevention produced by N omega-nitro-L-arginine methyl ester on the increased release of norepinephrine caused by Ang II and Ang-(1-7). The present results suggest that nitric oxide could be involved in the neuromodulatory function elicited by both Ang II and Ang-(1-7) in rat atria. The physiological role of this observation is still under study.
Gironacci
M M
MM
Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina.
Lorenzo
P S
PS
Adler-Graschinsky
E
E
D000803:Angiotensin I; D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D004347:Drug Interactions; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D009638:Norepinephrine / Q000378:metabolism*; D010446:Peptide Fragments / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013566:Sympathomimetics / Q000378:metabolism*
D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D013566:Sympathomimetics; D000804:Angiotensin II; D009569:Nitric Oxide; D000803:Angiotensin I; C118790:angiotensin I (1-7); D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine