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  • Title: Transport of d-galactose by the gastrointestinal tract of the locust, Locusta migratoria.
    Author: Pascual I, Berjón A, Lostao MP, Barber A.
    Journal: Comp Biochem Physiol B Biochem Mol Biol; 2006 Jan; 143(1):20-6. PubMed ID: 16314134.
    Abstract:
    Due to exoskeleton, the absorption of nutrients in adult insects takes place across the gastrointestinal tract epithelium. In most physiological studies, sugar intestinal absorption has been described as a diffusional process and to date no sugar transporter has been cloned from the digestive tract of insects. In the present work, the existence of a saturable transport system for galactose in the gastric caeca of Locusta migratoria is clearly demonstrated. This transport shows a relatively high affinity for galactose (apparent K0.5=2-3 mM) and is inhibited by glucose, 2-deoxyglucose and with less potency by fructose and alpha-methyl-d-glucoside. The absence of sodium or the presence of phloridzin hardly affects galactose absorption, indicating that it is not mediated by a SGLT1-like transporter. The absence of K+, Cl-, Mg2+ and Ca2+ or changes in the pH do not modify galactose absorption either. Nevertheless, phloretin, cytochalasin B and theophylline (inhibitors of facilitative transporters) decrease sugar uptake around 50%. Xenopus laevis oocytes microinjected with poly A+ RNA isolated from gastric caeca show sodium-independent galactose uptake that is three times higher than in non-injected oocytes, further supporting the existence of a mRNA coding for at least one equilibrative sugar transporter in L. migratoria gastric caeca.
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