Immunogold labeling study of the distribution of GLUT-1 and GLUT-4 in cardiac tissue following stimulation by insulin or ischemia

TY - JOUR

T1 - Immunogold labeling study of the distribution of GLUT-1 and GLUT-4 in cardiac tissue following stimulation by insulin or ischemia

AU - Davey, K A B

AU - Garlick, P B

AU - Warley, A

AU - Southworth, R

PY - 2007/4

Y1 - 2007/4

N2 - Whereas glucose transporter 1 (GLUT-1) is thought to be responsible for basal glucose uptake in cardiac myocytes, little is known about its relative distribution between the different plasma membranes and cell types in the heart. GLUT-4 translocates to the myocyte surface to increase glucose uptake in response to a number of stimuli. The mechanisms underlying ischemia- and insulin-mediated GLUT-4 translocation are known to be different, raising the possibility that the intracellular destinations of GLUT-4 following these stimuli also differ. Using immunogold labeling, we describe the cellular localization of these two transporters and investigate whether insulin and ischemia induce differential translocation of GLUT-4 to different cardiac membranes. Immunogold labeling of GLUT-1 and GLUT-4 was performed on left ventricular sections from isolated hearts following 30 min of either insulin, ischemia, or control perfusion. In control tissue, GLUT-1 was predominantly (76%) localized in the capillary endothelial cells, with only 24% of total cardiac GLUT-1 present in myocytes. GLUT-4 was found predominantly in myocytes, distributed between sarcolemmal and T tubule membranes (1.84 +/- 0.49 and 1.54 +/- 0.33 golds/mu m, respectively) and intracellular vesicles (127 +/- 18 golds/mu m(2)). Insulin increased T tubule membrane GLUT-4 content (2.8 +/- 0.4 golds/mu m P <0.05) but had less effect on sarcolemmal GLUT-4 (1.72 +/- 0.53 golds/mu m). Ischemia induced greater GLUT-4 translocation to both membrane types (4.25 +/- 0.84 and 4.01 +/- 0.27 golds/mu m, respectively P <0.05). The localization of GLUT-1 suggests a significant role in transporting glucose across the capillary wall before myocyte uptake via GLUT-1 and GLUT-4. We demonstrate independent spatial translocation of GLUT-4 under insulin or ischemic stimulation and propose independent roles for T-tubular and sarcolemmal GLUT-4

AB - Whereas glucose transporter 1 (GLUT-1) is thought to be responsible for basal glucose uptake in cardiac myocytes, little is known about its relative distribution between the different plasma membranes and cell types in the heart. GLUT-4 translocates to the myocyte surface to increase glucose uptake in response to a number of stimuli. The mechanisms underlying ischemia- and insulin-mediated GLUT-4 translocation are known to be different, raising the possibility that the intracellular destinations of GLUT-4 following these stimuli also differ. Using immunogold labeling, we describe the cellular localization of these two transporters and investigate whether insulin and ischemia induce differential translocation of GLUT-4 to different cardiac membranes. Immunogold labeling of GLUT-1 and GLUT-4 was performed on left ventricular sections from isolated hearts following 30 min of either insulin, ischemia, or control perfusion. In control tissue, GLUT-1 was predominantly (76%) localized in the capillary endothelial cells, with only 24% of total cardiac GLUT-1 present in myocytes. GLUT-4 was found predominantly in myocytes, distributed between sarcolemmal and T tubule membranes (1.84 +/- 0.49 and 1.54 +/- 0.33 golds/mu m, respectively) and intracellular vesicles (127 +/- 18 golds/mu m(2)). Insulin increased T tubule membrane GLUT-4 content (2.8 +/- 0.4 golds/mu m P <0.05) but had less effect on sarcolemmal GLUT-4 (1.72 +/- 0.53 golds/mu m). Ischemia induced greater GLUT-4 translocation to both membrane types (4.25 +/- 0.84 and 4.01 +/- 0.27 golds/mu m, respectively P <0.05). The localization of GLUT-1 suggests a significant role in transporting glucose across the capillary wall before myocyte uptake via GLUT-1 and GLUT-4. We demonstrate independent spatial translocation of GLUT-4 under insulin or ischemic stimulation and propose independent roles for T-tubular and sarcolemmal GLUT-4

U2 - 10.1152/ajpheart.00663.2006

DO - 10.1152/ajpheart.00663.2006

M3 - Article

SN - 1522-1539

VL - 292

SP - H2009 - H2019

JO - AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY

JF - AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY

IS - 4

ER -