The effect of the coupled oxidation of substrate on the permeability of blowfly flight-muscle mitochondria to potassium and other cations.
1. Blowfly flight-muscle mitochondria respiring in the absence of phosphate acceptor (i.e. in state 4) take up greater amounts of K(+), Na(+), choline, phosphate and Cl(-) (but less NH(4) (+)) than non-respiring control mitochondria. 2. Uptake of cations is accompanied by an increase in the volume of the mitochondrial matrix, determined with the use of [(14)C]-sucrose and (3)H(2)O. The osmolarity of the salt solution taken up was approximately that of the suspending medium. 3. The [(14)C]sucrose-inaccessible space decreased with increasing osmolarity of potassium chloride in the suspending medium, confirming that the blowfly mitochondrion behaves as an osmometer. 4. Light-scattering studies showed that both respiratory substrate and a permeant anion such as phosphate or acetate are required for rapid and massive entry of K(+), which occurs in an electrophoretic process rather than in exchange for H(+). The increase in permeability to K(+) and other cations is probably the result of a large increase in the exposed area of inner membrane surface in these mitochondria, with no intrinsic increase in the permeability per unit area. 5. No increase in permeability to K(+) and other cations occurs during phosphorylation of ADP in state 3 respiration.
D000818:Animals; D002247:Carbon Isotopes; D002712:Chlorides / Q000378:metabolism; D002794:Choline / Q000378:metabolism; D004175:Diptera; D066298:In Vitro Techniques; D008931:Mitochondria, Muscle / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D010084:Oxidation-Reduction; D010085:Oxidative Phosphorylation; D010539:Permeability; D010710:Phosphates / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism; D014316:Tritium; D014867:Water / Q000378:metabolism
D002247:Carbon Isotopes; D002712:Chlorides; D010710:Phosphates; D014867:Water; D014316:Tritium; D013395:Sucrose; D012964:Sodium; D002794:Choline; D011188:Potassium