Ion Transport in Mitochondria in the Context of Osmotic Concentration of the Buffer

Abstract

Studies on mitochondria has revealed apparent violation of the laws of osmosis, probably related to ion transport. In this context, we studied changes in the content of potassium, sodium, magnesium, and calcium in mitochondria from wheat (Triticum aestivumL.) roots incubated in the buffer without the substrate that contained 0.3 or 0.5 M sucrose as well as potassium, and phosphate. The most pronounced changes were observed for potassium. Potassium inflow into mitochondria was more active at 0.5 than 0.3 M sucrose. The direction of the cation transport depended on its content in the initial buffer. At the certain threshold level, the inflow was replaced with the outflow; this threshold was lower at 0.3 than 0.5 M sucrose. Magnesium was also released from mitochondria; its stable outflow was primarily observed at its lower initial content in the suspension at 0.3 rather than 0.5 M sucrose. These data showed that the apparent violation of laws of osmosis was false and resulted from ion transport. Passive ion transport as a possible mechanism of adaptation to osmotic properties of the external medium is discussed.