Selective Uptake of Radiochemical Impurities by Mitochondria

Abstract

WHEN using potassium-42 to trace the exchange of potassium in a suspension of non-metabolizing mitochondria from rat liver, specimens were obtained in which the specific activity of mitochondrial potassium appeared greater than the specific activity of the separated labelling medium. The radioactive material used was spectroscopically pure ⁴²K₂CO₃, which had been irradiated for one week at the Atomic Energy Research Establishment, Harwell. When measured on a M6 (‘20th Century Electronics’) Geiger-Müller counter, the apparent specific activity (counts/min./μequiv. potassium) of potassium on the labelled mitochondria was 1.5 times as great as that of potassium in the labelling solution (Table 1). On further investigation it was found that the decay of activity on the mitochondria corresponded to a half-life greater than 12.4 hr. (see Fig. 1).