Short chain fatty acids (SCFAs), produced in the gut by bacterial ferm
entation of carbohydrates, change intestinal motility by mechanisms as
yet unknown. This study examined the mechanism(s) of action of SCFAs
on contractility using isolated rat terminal ileum segments and isolat
ed ileal smooth muscle cells. Strip contractions were recorded under i
sometric conditions. Intracellular calcium concentration ([Ca2+]i) was
measured in single cells loaded with indo-1 penta-acetoxymethyl ester
(indo-1 AM). SCFAs (10(-9) to 10(-2) mol/l) induced concentration dep
endent contractions. The effect was not different among the individual
SCFAs. Exogenous acids (namely tartaric and citric acids) caused simi
lar responses as SCFAs, whereas sodium acetate had no effect. The cont
raction was not blocked by tetrodotoxin, atropine or hexamethonium, sh
owing that it was not mediated through a cholinergic pathway. Moreover
, removal of the mucosa or addition of procaine (a local anaesthetic)
to the bath did not change the SCFA induced contraction, while verapam
il (a calcium-channel antagonist) completely suppressed it. In additio
n, application of SCFAs to isolated heal myocytes evoked peaks in [Ca2
+]i inhibited by D 600 (a blocker of voltage dependent calcium channel
s). Taken together, these results suggest that the contractile respons
e stimulated by SCFAs in the rat terminal ileum could result from an a
cid sensitive calcium dependent myogenic mechanism.