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First published online July 20, 2007
Journal of Experimental Biology 210, 2754-2764 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.006114

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Mechanistic bases for differences in passive absorption

Shana R. Lavin¹, Todd J. McWhorter^1,2 and William H. Karasov^1,*

¹ Department of Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA
² School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, WA 6150, Australia

View larger version (37K): [in this window] [in a new window]   Fig. 1. (A) L-arabinose, (B) L-rhamnose and (3) 3-O-methyl-D-glucose injected (filled symbols, solid lines) and gavaged (unfilled symbols, broken lines) into rats (right panels) and pigeons (left panels) were cleared from the blood rapidly and mono-exponentially. Insets show probe concentrations for the final three blood sampling times (t=90, 150, 240 min) on a semi-logarithmic plot. Values are means ± s.e.m. (N=6).

View larger version (22K): [in this window] [in a new window]   Fig. 2. (A,B) Uptakes (relative to control tissues) of tracer amounts of putative paracellular probes in everted sleeves of intestine were not significantly self-inhibited (100 mmol l–1 of the probes themselves) or inhibited by D-glucose (100 mmol l–1). In pigeons (A), probe uptake normalized to control (100 mmol l–1 mannitol) was not significantly different from 100% in pigeons except that lactulose was significantly inhibited by itself. Significant inhibition of L-rhamnose (<100% of uptake for control treatment) was noted in rats (B) when 100 mmol l–1 D-glucose was present in solution. Asterisks indicate significantly less than 100% (P<0.02). Values are means ± s.e.m. (N=5–7 sleeves/treatment). (C,D) Raw uptakes (µl mg–1 min–1) of tracer amounts of D-glucose and putative paracellular probes in the presence of unlabeled mannitol (control), the probe itself or D-glucose in pigeons (C) and rats (D). There was no significant difference in D-glucose uptake between rats and pigeons (F1,8=0.62; P=0.45).

View larger version (6K): [in this window] [in a new window]   Fig. 3. Pigeons (filled bars) had significantly greater clearance (µl min–1 cm–1) of L-arabinose and L-rhamnose than rats (open bars) in loops of intestine. Duodenal clearance (µl min–1 cm–1) of larger probes (cellobiose: Mr=342.3; raffinose: Mr=594.5) was relatively low for both pigeons (filled bars) and rats (open bars). Raffinose clearance was negligible. Values are means ± s.e.m. (N=5–6 rats, 6 pigeons). See text for statistical comparisons.