phalloidine and benzamil

Sodium influx is tightly regulated in the cells of blood origin. Amiloride-insensitive sodium channels were identified as one of the main sodium-transporting pathways in leukemia cells. To date, all known regulatory pathways of these channels are coupled with intracellular actin cytoskeleton dynamics. Here, to search for physiological mechanisms controlling epithelial Na

Topics: Actin Cytoskeleton; Actins; Amiloride; Cell Membrane; Cell Membrane Permeability; Cytochalasin D; Epithelial Sodium Channel Blockers; Epithelial Sodium Channels; Humans; K562 Cells; Leukemia, Myeloid; Membrane Potentials; Microscopy, Fluorescence; Models, Biological; Patch-Clamp Techniques; Phalloidine; Sodium; Trypsin; Trypsin Inhibitors

1. Confocal microscopic studies of rat colonic mucosa showed that the pericryptal sheath surrounding distal colonic crypts is an effective barrier both to dextran and NaCl movement, whereas no such structure surrounds the caecal crypts. 2. The distal colonic pericryptal barrier was functionally demonstrated by accumulation of Sodium Green within the pericryptal space. After exposure to benzamil, Sodium Green accumulation was decreased. Fluorescein isocyanate-labelled dextran (FITC dextran; molecular mass 10000 Da) was accumulated in the crypt lumens and pericryptal spaces. Both dextran and Sodium Green accumulation were absent from the pericryptal zone surrounding caecal crypts. 3. Low dietary Na+ intake raised rat plasma aldosterone and stimulated distal pericryptal sheath growth and adhesiveness as shown by increased amounts of F-actin, smooth muscle actin, beta-catenin and E-cadherins in the pericryptal zone. It also raised the capacity of the distal colon to dehydrate against a high luminal hydraulic resistance. This linkage indicates that trophic effects on the colon resulting from a low Na+ diet are not confined solely to effects on transepithelial Na+ transport, but are observed in the pericryptal sheath. 4. A computer model of crypt function confirms that a pericryptal sheath with low permeability to NaCl is an essential component of the crypt dehydrating mechanism.

Topics: Actins; Aldosterone; Amiloride; Animals; beta Catenin; Biological Transport; Boron Compounds; Cadherins; Cecum; Cytoskeletal Proteins; Dextrans; Diet, Sodium-Restricted; Fluorescent Dyes; Intestinal Absorption; Intestinal Mucosa; Intestine, Large; Muscle, Smooth; Organic Chemicals; Phalloidine; Rats; Rats, Wistar; Sodium Chloride; Trans-Activators