Protein kinase G expression in the small intestine and functional importance for smooth muscle relaxation.
In functional experiments, the nitric oxide (NO) donor N-morpholino-N-nitroso-aminoacetonitrile or the cGMP analog 8-(4-chlorophenylthio)-cGMP caused a concentration-dependent, tetrodotoxin-resistant relaxation of precontracted strips from rat small intestine. The inhibitory effect of both substances was completely blocked at lower concentrations and was significantly attenuated at higher concentrations by the selective cGMP-dependent protein kinase (cGK) antagonist KT-5823 (1 microM). cGK-I was identified by immunohistochemistry in circular and longitudinal muscle, lamina muscularis mucosae, and smooth muscle cells of the villi and in fibroblast-like cells of the small intestine. Additionally, there was staining of a subpopulation of myenteric and submucous plexus neurons. Double staining for neuronal NO synthase (nNOS) and cGK-I demonstrated a colocalization of these two enzymes. Western blot analysis of smooth muscle preparations and isolated nerve terminals demonstrated that these structures predominantly contain the cGK-Ibeta isoenzyme, whereas the cGK-Ialpha expression is about threefold less. The isoform cGK-II was entirely confined to mucosal epithelial cells. These results show that cGK-I is expressed in different muscular structures of the small intestine and participates in the NO-induced relaxation of gastrointestinal smooth muscle. The presence of cGK-I in NOS-positive enteric neurons further suggests a possible neuronal action site.
Department of Internal Medicine II, Technical University of Munich, 81675 Munich, Germany.
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A
Huber
P
P
Trudrung
M
M
Storr
H
H
Franck
V
V
Schusdziarra
P
P
Ruth
H D
HD
Allescher
D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002227:Carbazoles; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D007211:Indoles / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000201:enzymology; D007421:Intestine, Small / Q000201:enzymology / Q000294:innervation / Q000502:physiology*; D008297:Male; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000201:enzymology / Q000294:innervation / Q000502:physiology*; D009197:Myenteric Plexus / Q000502:physiology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D016133:Polymerase Chain Reaction; D011758:Pyrroles / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013873:Thionucleotides / Q000494:pharmacology
D000470:Alkaloids; D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D020030:Nitric Oxide Donors; D011758:Pyrroles; D013873:Thionucleotides; C073601:KT 5823; C055656:8-((4-chlorophenyl)thio)cyclic-3',5'-GMP; C057416:KT 5720; C002385:linsidomine; D008981:Molsidomine; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP