Different properties of the paracellular pathway account for the regional small intestinal permeability to the peptide desmopressin.
The regional small intestinal permeability to the vasopressin analogue desmopressin (dDAVP) was further characterized in proximal jejunal and distal (ileocecal) segments of the rat. Administration of the peptide to closed small intestinal loops confirmed the existence of regional absorption differences also in vivo in rats. Thus, the extent of absorption was about 4 times as high from the ileocecal part of the small intestine. The mucosal to serosal passage of dDAVP was studied in small intestinal segments from rats, mounted in Grass diffusion chambers. Increasing the mucosal concentration of dDAVP 100-fold had no effect on permeability coefficients (Papp) and the regional permeability distal:proximal ratio was maintained. Excessive amounts of unlabeled dDAVP to reduce the passage of [3H]dDAVP had no effect either. These findings make the existence of an active, receptor-mediated transport mechanism unlikely, and dDAVP probably does not affect its own transport rate. The higher ileocecal permeability could either be due to the presence of more permeable or dynamic pores in this region, where the epithelial surface area is smaller, or to an increased capacity for paracellular water flux. These results may have relevance for drug transport in the small intestine, where site-specific delivery of drug or enhancing agents may be optimized.
Pantzar
N
N
Department of Animal Physiology, University of Lund, Sweden.
Lundin
S
S
Weström
B R
BR
D000818:Animals; D001693:Biological Transport, Active; D002463:Cell Membrane Permeability; D015638:Cytochalasin D / Q000494:pharmacology; D003894:Deamino Arginine Vasopressin / Q000097:blood / Q000493:pharmacokinetics*; D005947:Glucose / Q000494:pharmacology; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
D015638:Cytochalasin D; D003894:Deamino Arginine Vasopressin; D005947:Glucose