Cd-109 transport in rat brain

The brain distribution of (CdCl2)-Cd-109 following administration into eith er the tail vein, the lateral ventricle or the olfactory bulb was studied t o clarify permeability of the brain barrier system to cadmium (Cd) and Cd m ovement in the cerebrospinal fluid (CSF) and the brain extracellular fluid. One hour after intravenous (i.v.) injection,Cd-109 was largely concentrate d in the choroid plexus, and Cd-109 concentration in the major part of the brain parenchyma, except for the circumventricular organs such as the pinea l grand and the regions around them, was low. Six days after i.v. injection , Cd-109 concentration in the choroid plexus was still high, and Cd-109 was also defected highly in the pineal gland and small part around the median eminence. Cd-109 concentration in the major part of the brain parenchyma wa s decreased in parallel with that in the blood. In the case of injection of (CdCl2)-Cd-109 into the lateral ventricle, a large portion of Cd-109 was d etected in the ventricular system 6 days after injection, and Cd-109 concen tration in the major part of the brain parenchyma was less than the detecti on limit. These results suggest that Cd cannot easily get into the brain an d is blocked not only by the blood-brain and the blood-CSF barriers, but al so by the ependymal and pial surfaces. In the case of injection of (CdCl2)- Cd-109 into the olfactory bulb, a large portion of Cd-109 was detected in t he injected area 24 h after injection, and, the next 24 h later,Cd-109 dist ribution in the brain was not changed appreciably. These results suggest th at Cd cannot easily move in the brain extracellular space. and is taken up into the brain parenchyma. (C) 1999 Elsevier Science Inc.