Postnatal development of glucose transporter proteins in bovine skeletal muscle and adipose tissue

Facilitated diffusion of glucose across the plasma membrane is mediated by a family of glucose transporter (GLUT). GLUT I is ubiquitously present in a ll tissues and involved in cellular glucose uptake, while GLUT4 plays a key role in cellular glucose uptake stimulated by insulin in skeletal muscles and adipose tissue. To examine the postnatal change in the GLUTs of ruminan ts, the protein levels of GLUT1 and GLUT4 were measured by Western blot ana lysis of skeletal muscles. adipose tissue and brain of Holstein mate calves aged from 0 to 12 months. Analysis of rumen short chain volatile fatty aci ds revealed that rumen fermentation increased around 2-3 months old. The GL UT I level did not change in all tissues examined during the postnatal peri od. while the GLUT4 levels in skeletal muscle and subcutaneous adipose tiss ue decreased gradually, and at 12 month old, it was about 40% of those seen at 0 month old. These results are contrast to those in non-ruminant specie s, in which GLUT4 increases during postnatal development, and may be relate d to the insulin-resistance seen in adult ruminants.