Stimulatory effect of nitric oxide on bicarbonate secretion in bullfrog duodenums in vitro

Citation
O. Furukawa et al., Stimulatory effect of nitric oxide on bicarbonate secretion in bullfrog duodenums in vitro, DIGESTION, 60(4), 1999, pp. 324-331
Citations number
30
Categorie Soggetti
Gastroenerology and Hepatology","da verificare
Journal title
DIGESTION
ISSN journal
00122823 → ACNP
Volume
60
Issue
4
Year of publication
1999
Pages
324 - 331
Database
ISI
SICI code
0012-2823(199907/08)60:4<324:SEONOO>2.0.ZU;2-N
Abstract
The effect of nitric oxide (NO) on HCO3- secretion was examined in vitro us ing an isolated preparation of bullfrog duodenum. The tissue was bathed in unbuffered Ringer's solution gassed with 100% O-2 on the mucosal side and H CO3- Ringer's solution gassed with 95% O-2-5% CO2 on the serosal side. The HCO3- secretion was measured by the pH-stat method using 2 mmol/l HCl as th e titrant to keep the mucosal pH at 7.4. (+/-)-(E)-Ethyl-2-[(E)-hydroxyimin o]-5-nitro-3-hexenamine (NOR3) was used as a NO donor and added to the sero sal solution. To analyze the NOR3 action on HCO3- secretion, the effects of dibutyryl adenosine-3',5'-cyclic monophosphate (dbcAMP), dibutyryl guanosi ne-3',5'-cyclic monophosphate (dbcGMP), methylene blue, and indomethacin on the HCO, response were also examined. NOR3 (1 x 10(-4) and 3 x 10(-4) mol/ l) caused an increase in HCO3- secretion in a dose-dependent manner, and th is effect appeared with an about 30-min time lag, reaching the level of 1.5 -2.5 times greater than basal values at 1-2 h later. Both dbcAMP (1 x 10(-3 ) mol/l) and dbcGMP (1 x 10(-3) mol/l) also caused a significant increase i n HCO3- secretion in bullfrog duodenums in vitro, although the onset of the HCO3- response to dbcGMP was delayed as compared to the former. The stimul atory action of NOR3 on duodenal HCO3- secretion was significantly attenuat ed by methylene blue (5 x 10(-5) mol/l) and indomethacin (1 x 10(-5) mol/l) , the latter also inhibiting the HCO3- response to dbcGMP. The release of p rostaglandin E-2 in the serosal solution was significantly increased after addition of NOR3 (3 x 10(-4) mol/l) and dbcGMP (1 x 10(-3) mol/l) in an ind omethacin-sensitive manner. These results suggest that the NO donor increas es duodenal HCO3- secretion in vitro, and this action of NO donor is cGMP-d ependent and mediated by endogenous prostaglandins. Duodenal HCO3- secretio n may be regulated locally by NO/cGMP in addition to prostaglandin/cAMP.