IGF-I and insulin regulate glucose transport in mouse blastocysts via IGF-I receptor.
The roles of glucose deprivation, insulin, and insulin-like growth factor I (IGF-I) in the regulation of glucose transport in the mouse blastocyst were examined. Glucose transport, measured by uptake of 3-0-methyl glucose (3-OMG), was increased by 19% (P < 0.01) in response to glucose deprivation. Both IGF-I and insulin stimulated uptake, but IGF-I was 1,000-fold more potent than insulin, increasing uptake by 51% at 1.7 pM (P < 0.001). These effects began to appear after 20 min of incubation with growth factors, and required the simultaneous presence of glucose. The relative potencies of insulin and IGF-I suggest that the actions of IGF-I and insulin were both mediated via the IGF-I receptor. The inactivity of a specific agonistic insulin receptor antibody (B10) confirms this and suggests that this action may be independent of signalling through IRS-1. Cycloheximide decreased growth factor-stimulated transport by about 40%, indicating that both protein synthesis and transporter recruitment from cytoplasmic stores are responsible for maximal stimulation. These characteristics are consistent with GLUT1-facilitated glucose uptake and suggest that GLUT1 is the regulatable transporter in mouse blastocysts. Stimulation of GLUT1 may be a ubiquitous feature of the autocrine/ paracrine activity of IGF-I in cell growth and proliferation.
Pantaleon
M
M
Department of Physiology and Pharmacology, University of Queensland, Australia.
Kaye
P L
PL
D019325:3-O-Methylglucose / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001755:Blastocyst / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D005260:Female; D007328:Insulin / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D008297:Male; D051379:Mice; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D017526:Receptor, IGF Type 1 / Q000378:metabolism*
D007328:Insulin; D011500:Protein Synthesis Inhibitors; D019325:3-O-Methylglucose; D007334:Insulin-Like Growth Factor I; D003513:Cycloheximide; D017526:Receptor, IGF Type 1