title: Basolateral inositol transport by intestines of carnivorous and herbivorous teleosts.
abstract: Myoinositol transport by isolated basolateral membrane vesicles was characterized from intestines of the herbivorous tilapia (Oreochromis mossambicus) and the carnivorous eel (Anguilla anguilla). [3H]myoinositol transport occurred by nonelectrogenic, facilitated diffusion independent of cation gradients and was inhibited by phloretin (Ki = 0.6 and 0.9 mM for tilapia and eel, respectively) but not by phloridzin. Kinetic analysis of myoinositol influx disclosed no differences in concentration yielding half-maximal influx or maximum influx between these species. D-Glucose inhibition of myoinositol influx was shown to be noncompetitive. Additional inhibition studies with a range of sugars demonstrated that aldohexoses in the C-1 chair conformation were preferred substrates. Myoinositol had no inhibitory effect on D-glucose transport. Preloading vesicles with myoinositol transstimulated [3H]myoinositol uptake, while the use of internal D-glucose was without effect. These basolateral data support the contention that epithelial myoinositol carriers are separate from D-hexose transport systems present on the same membrane but are modulated by hexose binding to a regulator site on the myoinositol transporter. Furthermore, the comparison of two fish species suggests that genetic dietary transport adaptation occurs on the brush-border membrane, while no such adaptation is present at the epithelial basolateral pole.
authors.affiliation: Department of Zoology, University of Hawaii, Honolulu 96822.
authors.forename: S J
authors.initials: SJ
authors.lastname: Reshkin
authors.forename: S
authors.initials: S
authors.lastname: Vilella
authors.forename: G A
authors.initials: GA
authors.lastname: Ahearn
authors.forename: C
authors.initials: C
authors.lastname: Storelli
mesh_terms: D000811:Anguilla / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002241:Carbohydrates / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D005399:Fishes / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D007294:Inositol / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D009994:Osmolar Concentration; D010693:Phloretin / Q000494:pharmacology; D010695:Phlorhizin / Q000494:pharmacology
chemical_list: D002241:Carbohydrates; D007294:Inositol; D010695:Phlorhizin; D005947:Glucose; D010693:Phloretin