Guanosine di- and tri-phosphates in the phosphate metabolism of cerebral tissues promoted by electrical pulses.

In a previous communication (Heald, 1957 b) it was shown that the 'phosphoprotein' fraction of cerebral tissues was implicated in the rapid phosphateexchange reactions promoted by applied electrical pulses (Heald, 1956b). It was pointed out that owing to the crudeness of the analytical methods employed the nature of the phosphoprotein could not be determined, more especially since its estimation depended upon a preliminary degradation to inorganic phosphate. It was also considered that since the phospholipid fraction showed no change in specific radioactivity upon the passage of pulses, the phospholipids were not involved in the rapid-exchange reactions which were described. However, it was pointed out by Dr G. H. SloaneStanley and subsequently by Professor J. Folch that treatment of the tissue with trichloroacetic acid to remove phosphates soluble in this extractant before further fractionation would affect the extractability of the phospholipids, some of which might conceivably remain unextracted and be degraded to inorganic phosphate during the analysis for 'phosphoprotein'. For these reasons attempts were made to isolate from cerebral tissues, under conditions less degradative than those previously used, a phosphate fraction or fractions which increased in specific radioactivity when electrical pulses were applied for 10 sec. to tissue which had metabolized radioactive phosphate for a brief period. Such an increase in specific radioactivity under these conditions had previously been found to occur with the phosphoprotein fraction. This has led to the discovery that guanosine diand tri-phosphates are components of cerebral tissue implicated in this type of response. A preliminary account of this work was presented to the Biochemical Society in November 1956 (Heald, 1957 a).