The intestine, particularly the small bowel, represents a large surface (in the adult 2 human approximately 200m ) through which the body is exposed to its environment. A vigorous substrate exchange takes place across this large surface: nutrients and xenobiotics are absorbed from the lumen into the bloodstream or the lymph, and simultaneously, the same types of substrate pass back into the lumen. The luminal surface of the intestine is lined with a "leaky" epithelium, thus the passage of the substrates, in either direction, proceeds via both transcellular and intercellular routes. Simple and carrier-mediated diffusion, active transport, pinocytosis, phagocytosis and persorption are all involved in this passage across the intestinal wall. The term "intestinal permeation" refers to the process of passage of various substances across the gut wall, either from the lumen into the blood or lymph, or in the opposite direction. "Permeability" is the condition of the gut which governs the rate of this complex two-way passage. The pharmacologist's interest in the problem of intestinal permeation is twofold: on the one hand, this process determines thebioavailability of drugs and contributes significantly to the pharmacokinetics and toxicokinetics of xeno biotics; on the other hand, the pharmacodynamic effects of many drugs are manifested in a significant alteration of the physiological process of intestinal permeation.

1 Morphology of the Intestinal Mucosa.

2 Intestinal Permeation and Permeability: an Overview.
3 Permeability and Related Phenomena: Basic Concepts
4 Methods for Investigation of Intestinal Permeability
5 Vascular Perfusion of Rat Small Intestine for Permeation and Metabolism Studies
6 The Use of Isolated Membrane Vesicles in the Study of Intestinal Permeation
7 The Transport Carrier Principle
8 Energetics of Intestinal Absorption
9 Polarity of Intestinal Epithelial Cells: Permeability of the Brush Border and Basolateral Membranes
10 Electrical Phenomena and Ion Transport in the Small Intestine
11 Intestinal Permeation of Water
12 Intestinal Permeability to Calcium and Phosphate
13 Protein-Mediated Epithelial Iron Transfer
14 Intestinal Absorption of Heavy Metals
15 Intestinal Permeability of Water-Soluble Nonelectrolytes: Sugars, Amino Acids, Peptides
16 Pharmacologic Aspects of Intestinal Permeability to Lipids (Except Steroids and Fat-Soluble Vitamins)
17 Intestinal Absorption of the Fat-Soluble Vitamins: Physiology and Pharmacology.