EFFECTS OF HYPERTONIC SOLUTIONS AND OF MERCURIC CHLORIDE ON THE UPTAKE OF [14C]GLUCOSE ANALOGUES BY RABBIT BRAIN

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Abstract
Intracarotid perfusion of hypertonic solutions of urea, NaCl or acetamide increased the brain uptake index (BUI) of glucose analogues by rabbit brain, while isotonic urea was without effect. Lactamide, whether isotonic or hypertonic, decreased the BUI of glucose analogues. The increased BUI produced by the other hypertonic solutions could be inhibited by unlabeled substrate, unlabeled glucose or by phloridzin, and may reflect stimulated carrier‐mediated transport of monosaccharides into brain. Although the increases could also have been due to altered cerebral blood flow, radioautography showed no gross evidence of such alterations. The BUI of 2‐2‐deoxy‐D‐[1‐14C]glucose was decreased by intracarotid injection of 0.01mM HgCl2, to the same level seen following maximal inhibition with unlabeled 2‐deoxy‐D‐glucose, while 0.08mM HgCl2 gave BUI's above this level. The lower concentration of HgCl2 probably inhibited carrier‐mediated monosaccharide transfer, while the higher concentration appeared to increase passive diffusion into the brain as well.