SODIUM, POTASSIUM, NITROGEN, PHOSPHORUS, AND LIPID IN MUSCLE MITOCHONDRIA ISOLATED IN SUCROSE MEDIA OF VARYING CONCENTRATIONS

Mitochondrial pellets isolated in 0.25 M sucrose from pigeon breast muscle and washed once contained 77 ± 1.43 g water per 100 g pellet, 7.8 ± 2.0 meq K and 4.29 meq Na per kg dry weight. The Na:K ratio for mitochondria was almost 5 times that of muscle, suggesting that mitochondria might contain some of the "excess" sodium of skeletal muscle. A comparison of mitochondria isolated in three different sucrose media (0.25 M, 0.45 M, 0.88 M) was made with respect to sodium, potassium, and water concentrations of unwashed mitochondria (M1) and those washed once (M2). Washing always resulted in a loss of sodium and potassium but neither repeated washing nor suspension in hypotonic solutions removed all of the cations. These findings and the high concentration ratios observed between mitochondria and the suspension media attested to the presence of "bound" or restricted cations. A few analyses for nitrogen, phosphorus, and lipid made on the various mitochondrial preparations, on microsomal-like material, and on a "floating layer" believed to be washed out of M1 preparations by resuspension, drew attention to the possibility of altering the character of the unit of reference (dry weight, mg N, etc.) used for expressing concentrations of cations. The "floating layer" was unique in being high in lipid and high in sodium. Analytical data and electron micrographs provided evidence that 0.45 M sucrose preserved the chemical and morphological integrity of the mitochondria better than the other concentrations tested.