Rapid GLUT-1 mediated glucose transport in erythrocytes from the grey-headed fruit bat ( Pteropus poliocephalus)

Abstract

d-Glucose entry into erythrocytes from adult grey-headed flying fox fruit bats ( Pteropus poliocephalus) was rapid and showed saturation at high substrate concentrations. Kinetic parameters were estimated from the concentration dependence of initial rates of zero- trans d-glucose entry at 5.5°C as Michaelis constant ( K m) 1.64±0.56 mM, and maximal velocity ( V max) 1162±152 μmol·l·cell water −1·min −1. d-Glucose entry was inhibited by cytochalasin B; mass law analysis of d-glucose-displaceable cytochalasin B binding gave values of K d 37.1±5.0 nM and B max 361.2±9.1 pmol/mg membrane protein. Entry of 2-deoxy- d-glucose, and 3- O-methyl- d-glucose, into P. poliocephalus red cells was rapid, entry of d-fructose was very slow. Glucose transporter polypeptides were identified on immunoblots as a band M r 47 000–54 000 and their identity confirmed by d-glucose-sensitive photolabeling of membranes with [ 3H]-cytochalasin B. Peptide- N-glycanase F digestion of both human and bat erythrocyte membranes generated GLUT-1-derived bands M r 37 000. Trypsin digestion of human and fruit bat erythrocyte membranes generated fragmentation patterns consistent with similar GLUT-1 polypeptide structures in both species. Erythrocytes from adult Australian ghost bats ( Macroderma gigas), a carnivorous microchiropteran bat, also expressed high levels of GLUT-1 .