SUBSTRATE-STIMULATED OXYGEN-CONSUMPTION BY ISOLATED RAT-BRAIN MICROVESSELS IN THE PRESENCE AND ABSENCE OF ATP

We report here properties of isolated brain microvessels such as the r ate of oxygen consumption with different substrates; the permeabilizin g effect of added ATP is studied. With the isolation procedure present ed the cerebral endothelium has a metabolic activity comparable to tha t reported in the literature. The respiratory rate of the microvessels is not affected by the addition of ATP, whereas it is significantly i ncreased by addition of succinate and alpha-chetoglutarate. The exposu re of the isolated brain capillaries to ATP, in a Ca2+-free medium, in creases the uptake of 6-carboxyfluorescein. This may be due to pores o pened by ATP in the endothelial cell membrane in the absence of divale nt cations.