The transport of sugars across the perfused choroid plexus of the sheep.

Publisher Website
Google Scholar
Abstract
The blood-perfused choroid plexuses from the lateral ventricles of the sheep were used to determine the nature of sugar exchanges between blood and (CSF). There was a net entry of sugars from blood to CSF at all concentrations of sugars which were used and this net entry was seen when the sugars were measured either directly by enzymic analysis or by the use of isotopically labeled sugars. From competition experiments the order of affinity of the transporting system from both blood to CSF and CSF to blood was the same, i.e., 2-deoxy-D-glucose .mchgt. D-glucose > 3-0-methyl-D-glucose .mchgt. D-galactose. The transport of sugars from CSF to blood and blood to CSF consists in both cases of a non-saturable and a saturable component. The affinity of the 2 systems is markedly different, the blood to CSF being a system of low affinity and high capacity, while that of the CSF to blood has a high affinity and a low capacity. The concentration of glucose in the newly formed CSF was estimated from the rate of CSF secretion and the net flux of glucose across the choroid plexus. The concentration of glucose in this fluid was some 45-60% of that in plasma and so the low glucose concentration observed in bulk CSF would appear to be a result of the entry process and not that of cerebral metabolism.