NO and cGMP facilitate adenosine production in rat hearts via activation of ecto-5'-nucleotidase.
We examined whether nitric oxide (NO), a possible cardioprotective substance, can increase the production of interstitial adenosine in the ventricular myocardium. A flexibly mounted microdialysis technique was used to measure the concentration of interstitial adenosine and to assess the activity of ecto-5'-nucleotidase in in vivo rat hearts. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rats and perfused with Tyrode solution containing adenosine 5'-monophosphate (AMP) at a rate of 1.0 microl min-1. The concentration of adenosine in the effluent (dialysate) was measured by high-performance liquid chromatography. Dialysate adenosine obtained during perfusion with the AMP-containing solution through the probe originated from the hydrolysis of AMP by endogenous ecto-5'-nucleotidase, and the level of adenosine reflected the activity of ecto-5'-nucleotidase in the tissue. S-Nitroso-N-acetylpenicillamine (SNAP, 0.3-3 mM), an NO donor, increased the dialysate adenosine measured in the presence of AMP (100 microM) in a concentration-dependent manner. However, in the presence of an NO-oxidizing agent, 2-(4-carboxyphenyl-4,4,5, 5-tetramethylimidazoline)-1-oxyl 3-oxide (carboxy-PTIO, 1 mM), the effect of SNAP was abolished. Another NO donor, (+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (FK409, 1 mM) also increased adenosine production. 8-Bromo-cGMP (0.1-3 mM), a membrane-permeable cGMP analogue and a potent activator of cGMP-dependent protein kinase, increased the level of AMP-primed dialysate adenosine in a concentration-dependent manner. These results suggest that NO facilitates the production of interstitial adenosine in rat hearts in situ, via cGMP-mediated activation of ecto-5'-nucleotidase.
Obata
T
T
Department of Pharmacology, Oita Medical University, 1-1 Idaigaoka, Hasama, Oita 879-5593, Japan.
Sato
T
T
Yamanaka
Y
Y
Arita
M
M
D015720:5'-Nucleotidase / Q000378:metabolism*; D000241:Adenosine / Q000096:biosynthesis*; D000249:Adenosine Monophosphate / Q000008:administration & dosage / Q000378:metabolism; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D008297:Male; D017551:Microdialysis; D009206:Myocardium / Q000201:enzymology*; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009574:Nitro Compounds / Q000494:pharmacology; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D020030:Nitric Oxide Donors; D009574:Nitro Compounds; C110881:S-nitro-N-acetylpenicillamine; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D000249:Adenosine Monophosphate; C061872:FK 409; D015720:5'-Nucleotidase; D010396:Penicillamine; D006152:Cyclic GMP; D000241:Adenosine