M. Shetty et al., STIMULATION OF GLUCOSE-TRANSPORT IN CLONE-9 CELLS BY INSULIN AND THYROID-HORMONE - ROLE OF GLUT-1 ACTIVATION, Biochimica et biophysica acta. Molecular cell research, 1314(1-2), 1996, pp. 140-146
Thyroid hormone (T-3) and insulin are both shown ro stimulate glucose
transport in Clone 9 cells, a rat liver sell line in which the utiliza
tion of glucose is limited by transport rate and in which only tile GL
UT-1 transporter isoform is expressed. Pre-treatment of these cells wi
th T-3 moreover substantially enhances the stimulatory effect of insul
in such that at maximally effective hormone concentrations the effects
of T-3 and insulin on glucose transport are more than aciditive and i
ndeed nearly multiplicative suggesting that the mechanisms mediating t
he enhancement of glucose transport differ between the two hormones. t
ell surface biotinylation followed by Western-blot analysis of plasma
membrane fractions showed that the stimulatory effects of T-3 and insu
lin on glucose transporter, whether acting singly or in combination, e
xceed the attendant increases in the abundance of GLUT-I is the plasma
membrane. Ir is suggested that activation of GLUT-I molecules pre-exi
sting in the plasma membrane plays a major role ill mediating the stim
ulatory effects of T-3 and insulin on glucose transport in this cell l
ine.