Nitric oxide regulates the release of somatostatin from cultured gastric rabbit primary D-cells.
OBJECTIVE
Neuronal nitric oxide synthase (nNOS) is present in gastric D-cells. Mucosal somatostatin is diminished in H. pylori gastritis, where production of nitric oxide (NO) is increased. Therefore, we investigated the role of NO in D-cell function and the effects of prolonged exposure of D-cells to NO.


METHODS
Rabbit gastric D-cells were cultured. Somatostatin-14 was measured after 2 hours to examine the effects of arginine, nitric oxide sythase (NOS) inhibitors, and NO donors. Some cells were preincubated with a slow releasing NO donor for 12 hours. Results are expressed as percentage of total cell content. Nitrate content was measured by chemiluminescent assay.


RESULTS
L-arginine increased somatostatin-14 release in the presence of CCK8 from 4.4% +/- 0.5% to 6.4% +/- 0.4% (P < 0.02), and this was accompanied by NO release from 27 +/- 7 micromol/L to 86 +/- 12 micromol/L (P = 0.001). D-arginine and L-lysine had no effect. NOS inhibitors LNNA, SMT, and 7NI significantly attenuated the stimulatory response to L-arginine. NO donors sodium nitroprusside (SNP), 1 mmol/L, and S-nitroso-N-acetyl-D-L-penicillamine, 0.1 mmol/L, significantly increased basal and cholecystokinin-8 (CCK8) stimulated somatostatin release. Oxyhemoglobin attenuated the effect of SNP but not of L-arginine. Neither cyclic guanosine monophosphate nor guanylate cyclase were involved in the response to NO. However, inhibition of adenosine diphosphate (ADP) ribosyltransferase significantly decreased the response to L-arginine. Preincubation for 12 hours with 150 micromol/L (Z)-1-[(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate; IP3, inositol triphosphate decreased the 2-hour cellular response to CCK8 and SNP.


CONCLUSIONS
NO regulates rabbit D-cells. Acute exposure stimulates somatostatin mediated by ADP ribosylation, whereas long-term exposure reduces cellular responses to stimuli. The latter pathway may be responsible for the suppression of somatostatin in H. pylori gastritis.
Arebi
Naila
N
Department of Gastroenterology, Hammersmith Hospital, Imperial College School of Medicine, London, United Kingdom. naila.arebi@ic.ac.uk
Healey
Zoe V
ZV
Bliss
Philip W
PW
Ghatei
Mohammed
M
Van Noorden
Susan
S
Playford
Raymond J
RJ
Calam
John
J
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000502:physiology; D005753:Gastric Mucosa / Q000378:metabolism*; D007150:Immunohistochemistry; D009569:Nitric Oxide / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010108:Oxyhemoglobins / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D012844:Sincalide / Q000502:physiology; D013004:Somatostatin / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000596:Amino Acids; D020030:Nitric Oxide Donors; D010108:Oxyhemoglobins; D000246:Adenosine Diphosphate Ribose; D009569:Nitric Oxide; D013004:Somatostatin; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP; D012844:Sincalide