Mediated transport of chloride from blood into cerebrospinal fluid.

Abstract

The kinetics of transport of chloride from blood into CSF have been studied in the adult cat in vivo for a wide range of concentrations of chloride in arterial plasma: 1. In studies employing isosmotic replacement of body chloride with isethionate by means of extracorporeal hemodialysis, the chloride content in cerebral cortex and corpus callosum and concentration in CSF were relatively resistant to change despite the fact that plasma chloride was varied over the range 120.5 to 8.1 mM. 2. During hemodialysis the ratio of the concentration of chloride in CSF (or content in cerebral cortex) versus the concentration of chloride in arterial plasma was maintained for at least 1 or 2 h at as much as 10 times the ratios present in normal animals. 3. In studies with 36Cl, the rate of entry of chloride from blood into CSF followed Michaelis-Menten kinetics with the Vmax=0.55 μmole/ ml/min and with the Km < 60 mM and possibly < 8.1 mM. On the other hand the rate of entry of chloride from blood into cerebral cortex and corpus callosum was much slower and followed simple diffusion kinetics. 4. Evidence is presented indicating that chloride is transported from blood to CSP at the choroid plexus as well as at other sites. 5. On the basis of the rate of entry of chloride into CSF, the rate of bulk production of CSF in the adult cat was calculated to be 17.1 μl/min at normal plasma concentrations of chloride, a value in close agreement with previous estimates of the rate of production of CSF in the adult cat. 6. The relationships of the content of chloride in skeletal muscle and in liver to the concentration of chloride in plasma are presented, when the latter is varied over the range 120.5 to 8.1 mM.