ADENOSINE STIMULATES NITRIC-OXIDE SYNTHESIS IN RAT CARDIAC MYOCYTES

We investigated the effects of adenosine on nitric oxide (NO) synthesi s by measuring the production of nitrite, a stable metabolite of NO, i n cultured neonatal rat cardiac myocytes. Incubation of cultures with interleukin-1 beta (10 ng/ml) for 24 h caused a significant increase i n nitrite production. The interleukin-1 beta-induced nitrite productio n by cardiac myocytes was significantly increased by adenosine or its stable analog 2-chloroadenosine in a dose-dependent manner (10(-7)-10( -4) M). The adenosine A(2)-receptor antagonist KF-17837 (10(-6) M), bu t not the A(1)-receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (10(-6) M), significantly inhibited 2-chloroadenosine-mediated nitrite production. The 2-chloroadenosine-induced nitrite production by inter leukin-1 beta-stimulated cells was accompanied by inducible NO synthas e mRNA and protein accumulation. In the presence of N-6,2'-O-dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP) (10(-3) M) or isoprotereno l (10(-5) M), interleukin-1 beta-induced nitrite accumulation was furt her increased, but the effect of 2-chloroadenosine was not additive or synergistic. The protein kinase C inhibitor calphostin C did not inhi bit the effect of 2-chloroadenosine. These results indicate that adeno sine acts on Aa receptors and augments NO synthesis in interleukin-1 b eta-stimulated cardiac myocytes, at least partially through a cAMP-dep endent pathway.