Development of insulin sensitivity in rat skeletal muscle Studies of glucose transporter and insulin receptor mRNA levels

Expression of GLUT-4 and insulin receptor mRNAs was investigated in rat skeletal muscle by Northern hybridization. GLUT-4 mRNA was barely detectable in foetal muscle, was expressed at low levels by 1–8 days and at 2–3-fold higher levels during and after weaning (18–40 days). In contrast there was little change in insulin receptor mRNA levels prior to weaning and a reduction in mRNA abundance between 18 and 40 days. Weaning rats on to a diet rich in fat prevented the increase in GLUT-4 abundance seen between 15 and 29 days in animals weaned on a high-carbohydrate diet.