NO releases bombesin-like immunoreactivity from enteric synaptosomes by cross-activation of protein kinase A.
The effect of nitric oxide (NO) on the release of bombesin-like immunoreactivity (BLI) was examined in synaptosomes of rat small intestine. The NO donor S-nitroso-N-acetylpenicillamine (SNAP; 10(-7) to 10(-4) M) significantly stimulated BLI release. In the presence of the NO scavenger oxyhemoglobin (10(-3) M) or the guanylate cyclase inhibitor ODQ (10(-5) M), SNAP-induced BLI release was antagonized. In addition, SNAP increased the synaptosomal cGMP content and elevation of cGMP levels by zaprinast (3 x 10(-5) M), an inhibitor of the cGMP-specific phosphodiesterase (PDE) type 5, and increased basal and SNAP-induced BLI release. NO-induced BLI release was blocked by Rp-adenosine 3',5'-cyclic monophosphorothioate (3 x 10(-5) M and 10(-4) M), an inhibitor of the cAMP-dependent protein kinase A, whereas KT-5823 (3 x 10(-6) M) and Rp-8-(4-chlorophenylthio)-cGMP (5 x 10(-5) M), inhibitors of the cGMP-dependent protein kinase G, had no effect. Because cGMP inhibits the cAMP-specific PDE3, thereby increasing cAMP levels, the role of PDE3 was investigated. Trequinsin (10(-8) M), a specific blocker of PDE3, stimulated basal BLI release but had no additive effect on NO-induced release, suggesting a similar mechanism of action. These data demonstrate that because of a cross-activation of cAMP-dependent protein kinase A by endogenous cGMP BLI can be released by NO from enteric synaptosomes.
Kurjak
M
M
Department of Internal Medicine II, Technical University Munich, 81675 Munich, Germany.
Fritsch
R
R
Saur
D
D
Schusdziarra
V
V
Allescher
H D
HD
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001839:Bombesin / Q000378:metabolism*; D000242:Cyclic AMP / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006152:Cyclic GMP / Q000096:biosynthesis / Q000502:physiology; D017869:Cyclic GMP-Dependent Protein Kinases; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D019335:Nitroarginine / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D011688:Purinones / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013574:Synaptosomes / Q000378:metabolism*
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D010069:Oxadiazoles; D010726:Phosphodiesterase Inhibitors; D047428:Protein Kinase Inhibitors; D011688:Purinones; D011810:Quinoxalines; D019335:Nitroarginine; D009569:Nitric Oxide; D001120:Arginine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases; C011145:zaprinast; D006152:Cyclic GMP; D001839:Bombesin