D-glucose permeability in river lamprey (Lampetra fluviatilis) and carp (Cyprinus carpio) erythrocytes.
1. The transport of 3-O-methyl-D-glucose (3-OMG) in lamprey and carp erythrocytes was studied. 2. In lamprey erythrocytes the half-time for the equilibration of 3-OMG was fast, approx. 8 min. In contrast, the erythrocytes of carp were almost impermeable to 3-OMG, with a half-time for equilibration of 14.2 hr. 3. 3-OMG was taken up by lamprey erythrocytes both by facilitated diffusion and simple diffusion. The presence of carrier-mediated transport was indicated by saturation kinetics and by inhibition by phloretin. The Km and Vm of the saturable component of 3-OMG transport were 1.6 mmol/l and 12.4 mmol/kg packed cells/hr. 4. Since the 3-OMG transport in carp erythrocytes showed no sign of saturation kinetics, it appears to proceed by simple diffusion only. 5. These results suggest that, as for most other teleost fish so far studied, low glucose permeability is insufficient to maintain normal energy metabolism in carp erythrocytes. In contrast, in agnathans facilitated glucose transport seems to be quite effective.
Department of Zoology, University of Helsinki, Finland.
K
K
Tiihonen
M
M
Nikinmaa
D019325:3-O-Methylglucose; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism*; D002347:Carps / Q000097:blood*; D002463:Cell Membrane Permeability / Q000502:physiology*; D004912:Erythrocytes / Q000378:metabolism*; D007798:Lampreys / Q000097:blood*; D008757:Methylglucosides / Q000097:blood
D001786:Blood Glucose; D008757:Methylglucosides; D019325:3-O-Methylglucose