Expression of glucose transporter isoforms and the insulin receptor during hamster preimplantation embryo development.
During preimplantation development, embryos of many species are known to express up to five isoforms of the facilitative glucose transporter proteins (GLUT). Development of hamster blastocysts is inhibited by glucose. We therefore investigated GLUT isoform and insulin receptor (IR) expression in hamster preimplantation embryos cultured in glucose-free medium from the 8-cell stage onwards. We show that GLUT1, 3 and 8 mRNA are constitutively expressed from the 8-cell to the blastocyst stage. The IR is expressed from the morula stage onwards. Messenger RNA of the insulin-responsive GLUT4 was not detected at any stage. GLUT1 and 3 were localised by immunocytochemistry. GLUT1 was expressed in both embryoblast and trophoblast, in the latter, mainly in basal and lateral membranes directed towards the blastocoel and embryoblast. GLUT3 was exclusively localised in the apical membrane of trophoblast cells. We show that hamster preimplantation embryos express several GLUT isoforms thus closely resembling embryos of other mammalian species. Despite endogenous IR expression, the insulin-sensitive isoform GLUT4 was not expressed, indicating that the insulin-mediated glucose uptake known from classical insulin target cells may not be relevant for hamster blastocysts.
Tonack
Sarah
S
Department of Anatomy and Cell Biology, Martin Luther University Faculty of Medicine, Grosse Steinstrasse 52, 06097 Halle (Saale), Germany.
Ramin
Nicole
N
Garimella
Sireesha
S
Rao
Rajnish
R
Seshagiri
Polani B
PB
Fischer
Bernd
B
Navarrete Santos
Anne
A
D000818:Animals; D001755:Blastocyst / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division; D006224:Cricetinae; D047108:Embryonic Development / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D005947:Glucose / Q000494:pharmacology; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics*; D051272:Glucose Transporter Type 1 / Q000235:genetics; D051274:Glucose Transporter Type 3 / Q000235:genetics; D009028:Morula / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D011972:Receptor, Insulin / Q000235:genetics*
D051246:Glucose Transport Proteins, Facilitative; D051272:Glucose Transporter Type 1; D051274:Glucose Transporter Type 3; D012333:RNA, Messenger; D011972:Receptor, Insulin; D005947:Glucose