AJP - Gastrointestinal and Liver Physiology, Vol 272, Issue 3 498-G506, Copyright © 1997 by American Physiological Society
Intestinal absorption of sodium dodecyl sulfate in the rodent: evidence for paracellular absorption
A. Amelsberg, C. D. Schteingart, J. Stein, W. J. Simmonds, G. A. Sawada, N. F. Ho and A. F. Hofmann
Department of Medicine, University of California, San Diego 92092-0813, USA.
Experiments were performed to define the mechanism of intestinal absorption
of dodecyl sulfate (DS), an amphipathic organic anion whose chemical
structure resembles that of dodecanoate, a C12 fatty acid anion. With
jejunal segments perfused in single-pass fashion in the anesthetized rat,
steady-state absorption of DS was concentration dependent, with the
apparent permeability constant (P(app)) ranging from 4 to 22 x 10(-5) cm/s.
When DS concentration was held constant and net water absorption was
induced by decreasing perfusate osmolality, DS absorption increased in
direct proportion to water absorption, suggesting absorption by solvent
drag via the paracellular route. However, DS absorption continued even when
water secretion was induced by a hypertonic perfusate. Consequently, for
all experiments, DS absorption could be empirically described as the sum of
two terms: 1) absorption in the absence of water absorption (P(app) = 5.6 x
10(-5) cm/s) and 2) absorption induced by water movement [(delta
P(app)/delta water absorption) = 0.2 x 10(-5) cm x s(-1) x microl
segment(-1) x min(-1)]. In a polarized epithelial monolayer of renal
epithelial cells (Madin-Darby canine kidney cells), DS was absorbed
predominantly by a paracellular pathway, as the absorption rate increased
threefold when paracellular junction pore size was increased by the
addition of cytochalasin D. The calculated apparent radius was 2.9 A,
indicating that the cross section of the molecule, not its length,
determined the rate of absorption. It is concluded that absorption of DS in
the intact animal occurs slowly and mostly via the paracellular route,
because the fixed negative charge on the molecule retards rapid passive
entry into the enterocyte, as occurs with protonated fatty acids. That
absorption of DS persisted despite net water secretion suggests a low level
of transcellular absorption across the jejunal enterocyte also occurs.
