AJP - Gastrointestinal and Liver Physiology, Vol 253, Issue 2 171-G178, Copyright © 1987 by American Physiological Society
Short-chain fatty acid transport and its effects on ion transport by rabbit cecum
M. Hatch
Short-chain fatty acid (SCFA) metabolism and transport were examined in
vitro across isolated rabbit cecal epithelia whose primary function is
absorption of these solutes. This study shows that although there was some
low-level metabolism of SCFAs to ketone bodies by the isolated cecum, a
significantly higher oxygen consumption was sustained for a longer time
period by tissues incubated in glucose-containing salines. The cecum
supported a significant net secretory flux of acetate (J net Ac- = -1.13
+/- 0.13 mu eq X cm-2 X h-1) and propionate (J net Pr- = -0.61 +/- 0.14 mu
eq X cm-2 X h-1). This study also shows that glucose significantly enhanced
short-circuit current (Isc), tissue conductance (Gt), and sodium transport
across this tissue. Neither Ac- nor Pr- enhanced net sodium flux (J net
Ac-) but Pr- significantly reduced net chloride flux (J net Cl-), whereas
Ac- had no effect. The increase in Isc and Gt observed in the presence of
SCFAs was attributable to the presence of SCFA in the serosal bathing
solution alone. To explain the latter finding and the unexpected finding of
SCFA secretion, the existence of an electrogenic anion (HCO3-) secretory
pathway is postulated. It is suggested that this system can accommodate
SCFAs in vitro and that it is a Na+-dependent system located on the
basolateral membrane of the cecal cell.
