Estimates of Michaelis-Menten constants for the two membranes of the brain endothelium

Albert Gjedde, O Christensen

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

Abstrakt

Tracer studies on facilitated diffusion across the blood-brain barrier lead to the calculation of Michaelis-Menten constants that describe the rate of transport. However, the barrier consists of two endothelial cell membranes, and the relevance of single Michaelis-Menten constants in relation to the two cell membranes is unknown. We have formulated a model of two endothelial cell membranes and show that the measured Michaelis-Menten constants are simple functions of the properties of the individual membranes when transport across the endothelium is rapid (P1 greater than 10(-6) cm s-1). We also show that the Michaelis-Menten constants determined in tracer experiments describe facilitated diffusion in the steady state only if the two membranes have similar transport properties. As an application of this observation, we have examined three experimental studies that measure glucose transport in the steady state and show that the Michaelis-Menten constants for glucose transport calculated from the tracer experiments are equal to the constants calculated from the steady-state experiments. We conclude that the luminal and abluminal membranes of brain capillary endothelial cells have equal glucose transport properties.

OriginalsprogEngelsk
TidsskriftJournal of Cerebral Blood Flow and Metabolism
Vol/bind4
Udgave nummer2
Sider (fra-til)241-249
ISSN0271-678X
DOI
StatusUdgivet - jun. 1984
Udgivet eksterntJa

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