A spatial segregation of ion transport processes between crypt and sur
face epithelial cells is well-accepted and integrated into physiologic
al and pathophysiological paradigms of small and large intestinal func
tion: Absorptive processes are believed to be located in surface (and
villous) cells, whereas secretory processes are believed to be present
in crypt cells. Validation of this model requires direct determinatio
n of fluid movement in intestinal crypts. This study describes the ada
ptation of techniques from renal tubule microperfusion to hand-dissect
and perfuse single, isolated crypts from rat distal colon to measure
directly fluid movement. Morphologic analyses of the isolated crypt pr
eparation revealed no extraepithelial cellular elements derived from t
he lamina propria, including myofibroblasts. In the basal state, crypt
s exhibited net fluid absorption (mean net fluid movement = 0.34+/-0.0
1 nl . mm(-1). min(-1)), which was Na+ and partially HCO3- dependent.
Addition of 1 mM dibutyryl-cyclic AMP, 60 nM vasoactive intestinal pep
tide, or 0.1 mM acetylcholine to the bath (serosal) solution reversibl
y induced net fluid secretion (net fluid movement approximate to -0.35
+/-0.01 . nl . mm(-1). min(-1)). These observations permit speculation
that absorption is a constitutive transport function in crypt cells a
nd that secretion by crypt cells is regulated by one or more neurohumo
ral agonists that are released in situ from lamina propria cells. The
functional, intact polarized crypt described here that both absorbs an
d secretes will permit future studies that dissect the mechanisms that
govern fluid and electrolyte movement in the colonic crypt.