Oxygen uptake by liver strips in the absence of Na +

Abstract

The incubation of liver slices during three hours in media devoid of Na+, substituted to maintain osmolarity by mannitol, sucrose, glucose, Li+, K+ or Tris, produces inhibi­ tion of the oxygen uptake that is greatest with mannitol (66 % during the third hour), somewhat less with sucrose or glucose and inferior, and very similar, with any of the three other replacements.

After one hour of incubation in different Na+-free media, the succinate dehydro­ genase activity diminishes if the medium used contained mannitol, sucrose or glucose, all with a very low ionic strength.

If after prc-incubation of the slices in Na+-free medium, they are incubated in control medium with Na+, the oxygen uptake returns almost completely to normal when the substitute used in the pre-incubation was glucose, sucrose, Li+ or Tris. In the case of mannitol or K+ the inhibition of the oxygen uptake was irreversible.

The ionic composition of the external medium affects the cellular metabolism, besides by the absence of Na+, a factor common to all media employed, by the changes that can be induced in the intracellular medium, in enzyme systems or in cellular structures, according to the nature of the substance which has been choosen for the Na+ replacement. With mannitol, the greatest and more irreversible inhibition of oxygen uptake and of succinate dehydrogenase activity are accomplished, which, must be a consequence of some peculiar action of mannitol.