An unusual active hexose transport system in human and mouse preimplantation embryos.
In a metabolic study of human and mouse preimplantation embryos (preembryos), we measured glucose uptake and phosphorylation with nonradioactive 2-deoxyglucose (DG) as tracer. Initial experiments indicated an active hexose transport capacity, a property thought to be restricted in mammals to intestinal villi and kidney tubules [Baly, D. L. & Horuk, R. (1988) Biochim. Biophys. Acta 947, 571-590]. Significant findings are as follows: (i) During a 60-min incubation with a low level of DG, mouse blastocyst DG rose to levels up to 30 times that of the medium. (The intestinal active system does not transport DG [Crane, R. K. (1960) Physiol. Rev. 40, 789-825].) (ii) Active preembryo transport was not blocked (as it would have been in the intestine) by phlorizin [Alvarado, F. & Crane, R. K. (1962) Biochem. Biophys. Acta 56, 170-172 and Sacktor, B. (1989) Kidney Int. 36, 342-350] or by replacement of Na+ with choline+ or K+ [Crane (1960) and Sacktor (1989)]. (iii) Transport of DG was blocked by cytochalasin B (which is not true for the intestinal transporter). We conclude that a distinct active hexose transporter and at least one facilitated transporter are present in preembryos, perhaps appearing in tandem on different membranes during formation of the increasingly complex preembryo structure.
Chi
M M
MM
Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, MO 63110.
Manchester
J K
JK
Basuray
R
R
Mahendra
S
S
Strickler
R C
RC
McDougal
D B
DB
Lowry
O H
OH
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001755:Blastocyst / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism*; D005260:Female; D005307:Fertilization in Vitro; D019298:Glucose-6-Phosphate / Q000031:analogs & derivatives*; D005958:Glucosephosphates / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D051379:Mice; D009028:Morula / Q000378:metabolism*; D010766:Phosphorylation; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology
D005958:Glucosephosphates; C015785:2-deoxyglucose-6-phosphate; D019298:Glucose-6-Phosphate; D003847:Deoxyglucose; D012964:Sodium; D011188:Potassium