AJP - Gastrointestinal and Liver Physiology, Vol 252, Issue 4 506-G510, Copyright © 1987 by American Physiological Society
Mechanism of pH effect on oleic acid and cholesterol absorption in the rat
K. Chijiiwa and W. G. Linscheer
Previous experiments [K. Chijiiwa and W. G. Linscheer, Am. J. Physiol. 246
(Gastrointest. Liver Physiol. 9): G492-G499, 1984] have shown higher rates
of absorption of oleic acid (OA) and cholesterol (CH) from micellar
solutions perfused through segments of small bowel at pH 5.5 than at pH
6.5. Both solutions contained equal amounts of these lipids in addition to
sodium taurocholate (30 mM). It was hypothesized that there may be two
reasons to explain this observation. First, the micelles of one of the two
solutions (pH 6.5) became depleted of these lipids during the perfusion
procedure, while the micelles of the other solution (pH 5.5) were kept
saturated with these lipids by the presence of emulsified particles in the
perfusate. Second, the pH difference resulted in a much lower ratio of
protonated vs. ionized OA in the pH 6.5 solution. Most investigators assume
that primarily protonated fatty acid (FA) is absorbed and very little
ionized FA is absorbed. The purposes of the present study are to evaluate
further the factor of lipid saturation of the micelles by comparison of
rates of absorption from two partially lipid-depleted micellar solutions
containing equal amounts of OA and CH, in which the micelles of one
solution were much more lipid depleted than the micelles of the other. This
was caused by the pH difference. The second purpose is to evaluate the
effect of the pH-related difference in protonate vs. ionized OA on
absorption of OA from nonmicellar aqueous solutions.(ABSTRACT TRUNCATED AT
250 WORDS)
