Increased brain uptake and CSF clearance of 14C-glutamate in spontaneously hypertensive rats

Abstract

Blood-to-brain and blood-to-CSF transport kinetics of 14C-glutamate in the spontaneously hypertensive rats (SHR) were studied using the in situ brain perfusion technique. Also, clearance of 14C-glutamate from CSF of SHR was studied using the ventriculo-cisternal (VC) perfusion technique. Blood-to-brain and blood-to-CSF transport kinetics showed greater rate of maximal transport into both brain and CSF of SHR compared to normotensive Wistar Kyoto (WKY) rats (p>0.05). Uptake into CSF of WKY and uptakes into brains of WKY and SHR did not show any significant diffusion (K(d)) of 14C-glutamate (p<0.05). However, some diffusion of 14C-glutamate only into CSF of SHR was observed, 0.031+0.006 microl min(-1) g(-1). Clearance of 14C-glutamate from CSF was greater in the SHR (28.33+/-6.9 microl min(-1)) compared to that in WKY rats (19.42+/-4.7 microl min(-1)). However, 14C-glutamate uptake by brain from CSF side was not significantly different between SHR and WKY rats (p>0.05). These results suggest that the greater blood-to-brain and blood-to-CSF entry of 14C-glutamate during hypertension may be balanced by greater removal of 14C-glutamate from CSF back to blood.