Penetration and effects of glyphosate in isolated potato mitochondria
1993
Arnaud, L. | Ravanel, P. | Anding, C. | Tissut, M.
The penetration and effects of the sodium salt of glyphosate, N-(phosphonomethyl) glycine, in isolated potato tuber mitochondria were investigated. The penetration study required the measurement of the volume of mitochondrial water space and this measurement was repeatedly carried out using [14C]dextran giving a value of 3.53 microliters mg-1 protein. After a 15 minute incubation period with medium containing 1 micromolar or 1 mM glyphosate, without respiratory substrate, almost no product was found in the membrane pellet, after disruption of the organelles in distilled water. In contrast, glyphosate was found in the mitochondrial water in a range of concentrations close to the external medium concentration. These results show that, at least the diffusion equilibrium between the medium, the intermembrane space and the matrix area was readily reached for glyphosate. The greater part of the product penetrated during the first five minutes of the incubation period. The glyphosate content, in mitochondria operating at 25 degrees, was not changed by adding either substrate (state IV), or substrate + ADP (state III). The probability of an active glyphosate transport by the mitochondrial inner membrane was therefore very unlikely. Glyphosate, at a concentration as high as 50 mM, was unable to change the respiratory activities of isolated potato tuber mitochondria (oxygen consumption rate with different substrates, ADP/O, respiratory control values, etc.).
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