Lack of evidence in vivo for nitrergic inhibition by Escherichia coli (STa) enterotoxin of fluid absorption from rat proximal jejunum.
Fluid absorption from the proximal jejunum of the anaesthetised rat was measured in vivo by fluid recovery. As expected, heat stable (STa) enterotoxin from E. coli reduced fluid absorption. Neither intraperitoneal L-NAME, thought to inhibit a putative neurally mediated action of STa, nor similar doses of D-NAME, ameliorated the inhibitory effect on jejunal fluid absorption of STa. Luminally perfused 10 mM sodium nitroprusside (SNP) had no effect on fluid absorption when expressed per gram dry weight per hour but reduced fluid absorption when expressed per cm length per hour. Similarly, 80 but not 40 mg/Kg of L-NAME reduced fluid absorption when expressed per cm length per hour, while the same dose of D-NAME did not. L-NAME and SNP significantly increased the wet weight to dry weight and the length to dry weight ratio of perfused loops. We conjecture that smooth muscle relaxation caused by these compounds increases interstitial fluid volumes that can be misconstrued as changes in absorption when this is expressed per cm length or per tissue wet weight. When fluid absorption is expressed per gram dry weight of tissue, there is no evidence for a role of nitric oxide in normal or STa inhibited fluid absorption.
Nelson
Y B
YB
Laboratory of Gastrointestinal Physiology, Division of Neuroscience and Biomedical Systems, Institute of Biomedical and Life Sciences, Glasgow University, Glasgow G12, 8QQ, Scotland, Great Britain.
Pande
D
D
McCormick
J
J
Balloch
K J D
KJ
Lucas
M L
ML
D000818:Animals; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004768:Enterotoxins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D029968:Escherichia coli Proteins; D005260:Female; D007408:Intestinal Absorption / Q000187:drug effects*; D007583:Jejunum / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D009573:Nitrites / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism
D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D009573:Nitrites; C034151:heat stable toxin (E coli); D009599:Nitroprusside; D009569:Nitric Oxide; D019331:NG-Nitroarginine Methyl Ester