AJP - Gastrointestinal and Liver Physiology, Vol 256, Issue 3 501-G508, Copyright © 1989 by American Physiological Society

ARTICLES

Brush-border inositol transport by intestines of carnivorous and herbivorous teleosts

S. Vilella, S. J. Reshkin, C. Storelli and G. A. Ahearn
Departimento di Biologia, Universita di Lecce, Italy.

Transport characteristics of myoinositol by isolated brush-border membrane vesicles of two fish, the herbivorous tilapia (Oreochromis mossambicus) and the carnivorous eel (Anguilla anguilla), were measured. [3H]myoinositol uptake by vesicles of both fish was stimulated by a transmembrane Na gradient, was electrogenic, and was inhibited by phloridzin. Kinetic analysis of myoinositol influx disclosed species differences (tilapia, K = 0.15 mM, Jmax = 0.2 nmol.mg protein-1.min-1; eel, K = 2.6 mM, Jmax = 0.8 nmol.mg protein-1.min-1). 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 effect on D-glucose transport. Preloading vesicles with myoinositol transstimulated [3H]myoinositol uptake, while the use of internal D-glucose was without effect. These results suggest that the intestinal brush border may have a pathway for myoinositol transport entirely separate from that for D-glucose but inhibited by D-glucose via binding to a regulator site on the myoinositol transporter. Markedly dissimilar influx kinetic constants suggest possible differences in myoinositol needs by carnivorous and herbivorous fish.

This article has been cited by other articles:

				R. Aouameur, S. Da Cal, P. Bissonnette, M. J. Coady, and J.-Y. Lapointe SMIT2 mediates all myo-inositol uptake in apical membranes of rat small intestine Am J Physiol Gastrointest Liver Physiol, December 1, 2007; 293(6): G1300 - G1307. [Abstract] [Full Text] [PDF]