Regional heterogeneity of the insulin-sensitive GLUT4 and GLUT8 in the healthy myocardium.

Higher total protein expression of A) GLUT4 and lower B) GLUT8 content in the healthy atrial compared to ventricular myocytes. Top panels: representative Western blot from total lysate of isolated rat myocytes; calsequestrin (CLSQ) was used as a loading control; representative bands were obtained from the same membrane. Bottom panels: Mean ± SE of total GLUT protein content (values expressed relative to atria; n = 6/group); * P<0.05 vs. atria. GLUT: glucose transporters. Insulin stimulation increases C) GLUT4 and D) GLUT8 protein content in the healthy atrial myocytes. Top panels: representative Western blot from total lysate of isolated rat myocytes, calsequestrin (CLSQ) was used as a loading control. Bottom panels: Mean ± SE of total GLUT protein content (values expressed relative to basal atria; n = 8-11/group); # P<0.05 vs. basal. Insulin stimulates E) GLUT4 and F) GLUT8 trafficking to the atrial and ventricular cell surface. Top panels: representative Western blot. Bottom panels: Mean ± SE of cell surface GLUT protein content (values expressed relative to labeled basal atria; n = 3-4/group); # P<0.05 vs. basal; *P<0.05 vs. atria. Methods: Cell surface GLUT measured using biotinylated photolabeling technique in the intact perfused mouse heart. L: Labeled (cell surface fraction); UL: Unlabeled (intracellular fraction).