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  • Title: Tonic regulation of mouse ileal ion transport by nitric oxide.
    Author: Rao RK, Riviere PJ, Pascaud X, Junien JL, Porreca F.
    Journal: J Pharmacol Exp Ther; 1994 May; 269(2):626-31. PubMed ID: 7514221.
    Abstract:
    The possible role of nitric oxide (NO) in the regulation of intestinal ion transport was studied in isolated sheets of mouse ileum mounted in Ussing flux chambers. The competitive NO-synthase inhibitors NG-methyl-L-arginine (L-NMA), and NG-nitro-L-arginine (L-NNA) and the effects of NO released from acidified sodium nitrite solution were evaluated in tissues pretreated with guanethidine and atropine. Serosal L-NMA or L-NNA (10-300 microM), but not NG-methyl-D-arginine (D-NMA), produced a sustained concentration-related increase in short-circuit current (Isc) and potential difference (PD) with maximal Isc increases of 50.8 +/- 8.2 and 45.5 +/- 5.8 microAmps/cm2, respectively; mucosal application of L-NMA or L-NNA produced transient increases in Isc. The A50 (and 95% CL) values for serosal L-NMA and L-NNA were 25.6 (15.7-41.9) and 8.7 (5.1-14.9) microM, respectively. L-Arginine (0.1-10 mM), but not D-arginine, produced both a concentration-related reversal of L-NMA or L-NNA-induced increases in Isc. Additionally, pretreatment with L-arginine blocked the L-NMA or L-NNA effects, suggesting a competitive interaction. L-NMA-mediated increases in Isc were unaffected by bicarbonate-free buffer, whereas replacement of chloride ions with gluconate ions almost completely attenuated the response to L-NMA. Further, the effects of L-NMA or L-NNA were blocked by tetrodotoxin or chlorisondamine, suggesting neural actions involving ganglionic transmission.(ABSTRACT TRUNCATED AT 250 WORDS)
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