EFFECT OF POTASSIUM AND OUABAIN ON GLUCOSE METABOLISM BY FROG BRAIN *
EFFECT OF POTASSIUM AND OUABAIN ON GLUCOSE METABOLISM BY FROG BRAIN *
复制标题
钾和哇巴因对青蛙脑葡萄糖代谢的影响 *
DOI：
10.1111/j.1471-4159.1965.tb04259.x
复制
发表时间：
1965
影响因子：
4.7
通讯作者：
José A. Zadunaisky
中科院分区：
文献类型：
--
作者：
Marta M. De Piras;José A. Zadunaisky
THE stimulating effect of potassium on brain respiration was described many years ago by several authors (ASHFORD and DIXON, 1935; DICKENS and GREVILLE, 1935). The increased respiration is concomitant with a stimulation of the citric acid cycle and may be inhibited by malonate, as shown by TSUKADA and TAKAGUCHI (1955). In normal brains, however, malonate has no effect on the respiration. This might suggest that probably the citric acid cycle is not the only one involved in the oxidation of substances. Recently, HOTTA (1962) was able to demonstrate that glucose is partially oxidized in mammalian brain slices via the pentose shunt pathway, but only when exogenous NADP and GSSG were added. In fact, in preliminary observations we found that a potent pentose shunt pathway for the oxidation of glucose existed in isolated whole frog brains in the absence of exogenous NADP and GSSG. The frog brain preparation has some advantages over mammalian brain slices. During incubation in Ringer solution similar to those used in this study, the maximal swelling of the frog brain amounted to an increase of 7 per cent in the wet weight after 5 hr, while Na and K contents did not show appreciable modifications. In these cases, glucose was the only substrate added to the medium. Furthermore, a steady state for sodium ions and an excellent preservation of the ultrastructure of the isolated frog brains have been shown after prolonged incubations under similar conditions (ZADUNAISKY and CURRAN, 1963 ; ZADUNAISKY, WALD and DE ROBERTIS, 1963). The lack of gross swelling of, and potassium loss from, frog brain in vitro can be taken as indications of excellent diffusion of oxygen and CO, throughout this preparation. These properties of the isolated frog brain offer a good opportunity for metabolic studies, an example of which is given in the present communication. This paper reports studies on the rate of oxidation of radioactive glucose labelled in the 1 or 6 positions by whole frog brains in vitro, or by homogenates of this tissue stimulated by potassium or inhibited by ouabain.
