In this study we have found that L-glutamic acid, as well as being taken up by a Na+-dependent mechanism, will stimulate the uptake of 22Na+ by primary astrocyte cultures from rat brain in the presence of ouabain. By simultaneously measuring the uptake of 22Na+ and L-3H-glutamate a stoichiometry of 2-3 Na+ per glutamate was measured, implying electrogenic uptake. Increasing the medium K+ concentration to depolarize the cells inhibited L-3H-glutamate uptake, while calculations of the energetics of the observed L-3H-glutamate accumulation also supported an electrogenic mechanism of at least 2 Na+:1 glutamate. In contrast, kinetic analysis of the Na+ dependence of L-3H-glutamate uptake indicated a stoichiometry of Na+ to glutamate of 1:1, but further analysis showed that the stoichiometry cannot be resolved by purely kinetic studies. Studies with glutamate analogs, however, showed that kainic acid was a very effective stimulant of 22Na+ uptake, but 3H-kainic acid showed no Na+ -dependent uptake. Furthermore, while L-3H-glutamate uptake was very sensitive to lowered temperatures, glutamate-stimulated 22Na+ uptake was relatively insensitive. These results indicate that glutamate-stimulated uptake of 22Na+ in primary astrocytes cultures cannot be explained solely by cotransport of Na+ with glutamate, and they suggest that direct kainic acid-type receptor induced stimulation of Na+ uptake also occurs. Since both receptor and uptake effects involve transport of Na+, accurate measurements of the Na+ :glutamate stoichiometry for uptake can only be done using completely specific inhibitors of these 2 systems.

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1. Methods of preparation of three distinct fractions of histones have been described and applied to the thymus, spleen and liver of calves and to the liver and spleen of normal and leukaemic rats. 2. No differences in amino acid composition or in N-terminal groups of the same fractions from the different sources were found, outside the probable experimental errors. On the other hand the characteristic analytical differences between the fractions were apparent in all the preparations. 3. The purity of the fractions was examined by starch-gel electrophoresis. Apart from minor bands observed in some cases and probably due to unremoved impurities, no differences of the patterns or of the mobilities were observed which could be ascribed to tissue or species specificity. 4. Some qualification of the above statements are necessary for fractions derived from the Ehrlich ascites tumour. A complete resolution into the fractions was not achieved in this case. We are indebted to the World Health Organization for the award of a Research Fellowship to one of us (L. H.) and to Dr V. Holoubek who made available the histones from leukaemic rat spleen and liver which he had prepared. We also wish to thank Dr D. M. P. Phillips for useful discussions. This investigation has been supported by grants to the