Segmental differences along the crypt axis in the response of cell volume to secretagogues or hypotonic medium in the rat colon.

VIP caused a decrease in the diameter of rat colonic crypts. This decrease was followed by a volume increase at the middle and the upper third of the crypt, which finally led to an increase of crypt diameter above the initial control values. At the fundus only a cell shrinkage was observed. The volume increase at the upper parts of the crypt was suppressed by the inhibitor of the Na(+)-K(+)-Cl(-)-cotransporter, furosemide. When crypts were exposed to a hypertonic medium, cell shrinkage was followed by a regulatory volume increase at the middle and the upper third of the crypt but not at the fundus region. These results suggest a gradient in the distribution of the Na(+)-K(+)-Cl(-)-cotransporter along the crypt axis.