Oxalate transport across the isolated rat colon. A re-examination.

A net absorption of oxalate and chloride was observed when isolated, short-circuited segments of rat colon were bathed by a calcium-containing buffer. Removal of calcium promoted a two-fold decrease in transmural resistance, while the net chloride flux was reduced and the net oxalate transport abolished. It was concluded that net oxalate absorption was not observed in previous studies (employing calcium-free buffers) because calcium is reqiured to maintain the integrity of the conductive pathways across colonic epithelia.