Ions and water in the epithelial cells of rabbit descending colon.

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Abstract
Isolated sheets of rabbit descending colon epithelial cells stripped from their underlying muscle coats were incubated in chambers at 37.degree. C with oxygenated media, and their non-inulin space water, Na, K and Cl contents were subsequently determined. With Na Ringer bathing both surfaces, amiloride, 10-4 M, decreased non-inulin space Na content by 76 mmol/kg dry wt. Ouabain, 10-3 M, caused loss of non-inulin space K which was not completely compensated for by uptake of Na over 30 min incubation. Cl and water decreased. Amiloride, 10-4 M, inhibited but did not prevent this uptake of Na after ouabain. Tissues exposed to Na-free choline Ringer rapidly exchanged non-inulin space Na for choline and, more slowly, lost K, Cl and water. The equilibration of Na in the non-inulin space when Na Ringer was restored to the mucosal medium alone was largely amiloride-insensitive. For restoration of non-inulin space K to normal levels, Na was required in the serosal but not the mucosal medium. Neither the absence of glucose nor the absence of Cl from the mucosal medium affected the non-inulin space sodium content when Na was restored to the mucosal medium bathing Na-depleted tissues. Whereas non-inulin space K and water contents are synonymous with their cellular values, only about 1/3 of non-inulin space Na is cellular when Na Ringer bathes both surfaces, and the concentration of the Na within the cellular transport pool approximated 20 mmol/kg H2O, consistent with estimates obtained from other techniques.