Cations and the mammalian brain.

A water insoluble fraction was prepared from ox cerebrum by homogenistation in water, dialysis against water, filtration and drying in air at 20-24°C. The fraction represented 15.5% +/- 3% (n = 8) of the weight of the fresh brain. The concentration of lipids was measured in fresh dried tissue, and also in the insoluble fraction. The insoluble fraction contained a mean of 81% (n = 6) of the lipids present in the fresh dried tissue, and 46% (n = 5) by the biuret method or 51% (n = 3) by the method of Lowry et. al., (1951) of the protein originally present. The Na+ and K+ concentrations were measured by atomic emission and absorption flame photometry, firstly in prepared media, and then in the same media after 4 ml of each of them had been mixed with lg of the insoluble fraction and left at 37 °C for 20 minutes; the concentration in the fraction was calculated from that found in the supernatant. When the insoluble fraction was mixed with Krebs-Ringer saline containing bicarbonate and glucose, modified so that the ratios of NaCl and KCl varied - (but together always added up to 150 mM) - the concentration of Na+ and K+ in the fraction was a mean of 2.6 times that present in the supernatant, when they contained Na+ or K+ up to 80 mM. When the concentrations of the cations in the media exceeded 80 mM, the concentration of Na+ in the fraction rose to a mean of 266 muMol/g, while the concentration of K+ fell to approximately zero. When only CaCl[2] or only MgSO[4] - or both salts - was omitted from the Krebs-Ringer bicarbonate glucose saline, the fraction did not take up any Na+ or K+ from the media at any concentration. The fraction did not take up any significant volume of oxygen, measured manometrically, either in the modified Krebs-Ringer solutions or in a mitochondrial substrate. The addition of AMP (2-5mM), ADP (2.5mM), ATP (2.5-5 mM), acetylcholine (0.01 - 200 muM), atropine (0.01 muM), eserine (30 muM), adrenaline (0.30 -30. muM ), nor-adrenaline (0.3 muM), ergotamine (10 muM), glutamate (2.5 mM) and ouabain (0.1 muM) with all the other constituents of modified Krebs-Ringer solution to the insoluble fraction, had significant effects on the uptake of Na+ and K+ by the fraction. The adenine nucleotides, nor-adrenaline, glutamate and ouabain, at the above concentrations, completely destroyed the affinity of Na+ and K+ for the insoluble fraction; whereas with acetylcholine, adrenaline and other related compounds, the uptake of Na+ and K+ was highly dependent on the concentration of the above substance and also of Na+ and K+, present in the media. A filtrate of the homogenised brain destroyed the affinity of Na+ and K+for the insoluble fraction