Stimulatory effect of nitric oxide on bicarbonate secretion in bullfrog duodenums in vitro.
The effect of nitric oxide (NO) on HCO-3 secretion was examined in vitro using an isolated preparation of bullfrog duodenum. The tissue was bathed in unbuffered Ringer's solution gassed with 100% O2 on the mucosal side and HCO-3 Ringer's solution gassed with 95% O2-5% CO2 on the serosal side. The HCO-3 secretion was measured by the pH-stat method using 2 mmol/l HCl as the titrant to keep the mucosal pH at 7.4. (+/-)-(E)-Ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamine (NOR3) was used as a NO donor and added to the serosal solution. To analyze the NOR3 action on HCO-3 secretion, the effects of dibutyryl adenosine-3',5'-cyclic monophosphate (dbcAMP), dibutyryl guanosine-3',5'-cyclic monophosphate (dbcGMP), methylene blue, and indomethacin on the HCO-3 response were also examined. NOR3 (1x10(-4) and 3x10(-4) mol/l) caused an increase in HCO-3 secretion in a dose-dependent manner, and this 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 (1x10(-3) mol/l) and dbcGMP (1x10(-3) mol/l) also caused a significant increase in HCO-3 secretion in bullfrog duodenums in vitro, although the onset of the HCO-3 response to dbcGMP was delayed as compared to the former. The stimulatory action of NOR3 on duodenal HCO-3 secretion was significantly attenuated by methylene blue (5x10(-5) mol/l) and indomethacin (1x10(-5) mol/l), the latter also inhibiting the HCO-3 response to dbcGMP. The release of prostaglandin E2 in the serosal solution was significantly increased after addition of NOR3 (3x10(-4) mol/l) and dbcGMP (1x10(-3) mol/l) in an indomethacin-sensitive manner. These results suggest that the NO donor increases duodenal HCO-3 secretion in vitro, and this action of NO donor is cGMP-dependent and mediated by endogenous prostaglandins. Duodenal HCO-3 secretion may be regulated locally by NO/cGMP in addition to prostaglandin/cAMP.
Department of Pharmacology and Experimental Therapeutics, Kyoto Pharmaceutical University, Kyoto, Japan.
O
O
Furukawa
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M
Kitamura
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S
Sugamoto
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K
Takeuchi
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D046508:Culture Techniques; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism; D004386:Duodenum / Q000187:drug effects* / Q000378:metabolism*; D007213:Indomethacin / Q000494:pharmacology; D008751:Methylene Blue / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D011892:Rana catesbeiana
D001639:Bicarbonates; D020030:Nitric Oxide Donors; D000242:Cyclic AMP; D006152:Cyclic GMP; D015232:Dinoprostone; D008751:Methylene Blue; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin