title: The effect of Escherichia coli STa enterotoxin and other secretagogues on mucosal surface pH of rat small intestine in vivo.
abstract: The mucosal surface pH of rat small intestine was measured in vivo. The surface pH in the normal jejunum was 6.20 +/- 0.02 (67) and 7.00 +/- 0.05 (5) in the ileum. Escherichia coli STa toxin induced a rapid and reversible alkalinization of both jejunal and ileal mucosae to a pH of 6.91 +/- 0.08 (10) and 7.67 +/- 0.06 (5) respectively. The synthetic ST analogue, STh-(6-19), had an effect identical to native STa toxin on jejunal surface pH. Theophylline (20 mM) maintained the STa-elevated jejunal surface pH after toxin removal but had no effect on untreated tissue. 8-Bromo cyclic GMP resembled STa by causing similar mucosal alkalinization in the jejunum; 8-bromo cyclic AMP, forskolin and cholera toxin individually had considerably smaller effects on surface pH, although combining forskolin or cholera toxin with theophylline resulted in alkalinization of the jejunal mucosa to a pH of 6.92 +/- 0.03 (5) and 6.76 +/- 0.04 (4). These results indicate that cyclic-GMP-dependent secretory processes are more capable of inducing surface pH changes than those dependent on cyclic AMP. The ability of STa to alter mucosal surface pH makes it a useful tool to investigate the microclimate hypothesis for weak electrolyte absorption.
authors.affiliation: Institute of Physiology, University of Glasgow, U.K.
authors.forename: G T
authors.initials: GT
authors.lastname: McEwan
authors.forename: H
authors.initials: H
authors.lastname: Daniel
authors.forename: C
authors.initials: C
authors.lastname: Fett
authors.forename: M N
authors.initials: MN
authors.lastname: Burgess
authors.forename: M L
authors.initials: ML
authors.lastname: Lucas
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology*; D002772:Cholera Toxin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004768:Enterotoxins / Q000494:pharmacology*; D029968:Escherichia coli Proteins; D006863:Hydrogen-Ion Concentration; D007082:Ileum / Q000187:drug effects / Q000502:physiology*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D007583:Jejunum / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008297:Male; D008839:Microelectrodes; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D013806:Theophylline / Q000494:pharmacology
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; C034151:heat stable toxin (E coli); D005576:Colforsin; C016276:8-bromocyclic GMP; D002772:Cholera Toxin; D013806:Theophylline; D006152:Cyclic GMP