Simple diffusive-convective model for intestinal absorption of a nonelectrolyte (urea)

Abstract

The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.

Transport Across Small Intestine

“…In human and canine small intestine the movements of small hydrophilic molecules such as urea, xylose and arabinose appear to be significantly influenced by solvent-drag or convective flow, and the "apparent" reflection coefficients 4 of these molecules are significantly less than unity (LEVITT et aI., 1969;LIFSON and HAKIM, 1966;HAKIM and LIFSON, 1964;FORD-TRAN et aI., 1968). The reflection coefficients are consistent with the notion that these solutes are entrained in a fluid stream that traverses pathways with equivalent pore radii of 7-15 A.…”

Intestinal absorption and presystemic disposition of sildenafil citrate in the rabbit: evidence for site-dependent absorptive clearance

“…The effect of net water flux on the absorptive clearance of sildenafil was studied according to Lifson's model [18]. Figure 2 represents a plot of sildenafil absorptive clearance versus the net water flux both normalized to the segment length at steady state for the different intestinal segments.…”

“…Separation was achieved using a 15 cm  3.9 mm (i.d.) C 18 , m Bondapak TM , Waters, reversed phase column with an average particle size of 10 mm, and the column was kept at ambient temperature. The column effluent was monitored at 240 nm and the chromatographic data analysis was performed with the Millenium TM Program (Waters, USA).…”

“…The net amount of drug absorbed per unit time can be described as the sum of two terms; the diffusive contribution and the convective contribution corresponding to the solvent drag effect. The net amount of drug absorbed per unit time is then given by the following equation [18][19][20].…”

Correlation between Net Water Flux and Absorptive Clearance Determined from In Situ Intestinal Perfusion Studies Does Not Necessarily Indicate a Solvent Drag Effect

“…1,2 The equation that describes such a correlation, partitioning intestinal absorption into diffusive and convective terms, is as follows: 3,4 PeA ¼…”