Possible Importance of Adenylate Cyclase Signaling Pathway in the Synthesis of Nitric Oxide by Myometrium Mitochondria

NO synthase activity (mtNOS) in uterine smooth muscle mitochondria under the action of the cAMP/protein kinase A signaling system modulators was studied. The experiments were performed on isolated mitochondria from rat myometrium using the NO-sensitive fluorescent probe DAF-FM-DA. NO synthesis in mitochondria was increased by adenylate cyclase activators NaHCO3 (30 mM) and forskolin (10 μM), as well as phosphodiesterase inhibitor caffeine (1 mM). The addition of ATP (0.5-5 mM) caused a slight increase in nitric oxide synthesis. The effect of ATP was enhanced in the presence of NaHCO3 and caffeine. The intensity of NO formation in mitochondria decreased by approximately 50 % in the case of inhibition of adenylate cyclase activity by the compound KH7 (25 μM). In the presence of the protein kinase A inhibitor PKI (10 nM) NO synthesis in mitochondria was also significantly reduced. When the constitutive NO-synthase inhibitor L-NAME (100 μM) was introduced into the incubation medium, the stimulating effect of the studied compounds on NO synthesis in mitochondria was not observed. These data suggests a possible dependence of mtNOS function on the activity of the cAMP/protein kinase A signaling system in smooth muscle mitochondria.