title: Functional characterization of a putative disaccharide membrane transporter in crustacean intestine.
abstract: Transepithelial absorption of dietary sucrose in the American lobster, Homarus americanus, was investigated by mounting an intestine in a perfusion chamber to characterize mucosal to serosal (MS) (14)C-sucrose transport. These fluxes were measured by adding varying concentrations of (14)C-sucrose to the perfusate and monitoring their appearance in the bathing solution. Transepithelial (14)C-sucrose transport was the combination of a hyperbolic function of luminal concentration, following Michaelis-Menten kinetics, and apparent diffusion. The kinetic constants of the putative sucrose transporter were KM = 20.50 ± 6.00 µM and J max = 1.81 ± 0.50 pmol/cm(2) × min. Phloridzin, an inhibitor of Na(+)-dependent mucosal glucose transport, decreased MS (14)C-sucrose transport. Decreased MS (14)C-sucrose transport also occurred in the presence of luminal trehalose, a disaccharide containing D-glucose moieties. Thin-layer chromatography (TLC) identified the chemical nature of radioactively labeled sugars in the bath following transepithelial transport. TLC revealed (14)C-sucrose was transported across the intestine largely intact with no (14)C-glucose or (14)C-fructose appearing in the serosal bath or luminal perfusate. Only 13% of bath radioactivity was volatile metabolites. Results suggest that disaccharide sugars can be transported intact across crustacean intestine and support the occurrence of a functional disaccharide membrane transporter.
authors.affiliation: Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL, 32224, USA.
authors.forename: Rasheda
authors.initials: R
authors.lastname: Likely
authors.forename: Eric
authors.initials: E
authors.lastname: Johnson
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Ahearn
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002855:Chromatography, Thin Layer; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008121:Nephropidae / Q000378:metabolism*; D010695:Phlorhizin / Q000494:pharmacology; D013395:Sucrose / Q000378:metabolism*; D014199:Trehalose / Q000378:metabolism
chemical_list: D026901:Membrane Transport Proteins; D013395:Sucrose; D014199:Trehalose; D010695:Phlorhizin